EMI filtered co-connected hermetic feedthrough, feedthrough capacitor and leadwire assembly for an active implantable medical device

ABSTRACT

A co-connected hermetic feedthrough, feedthrough capacitor, and leadwire assembly includes a dielectric substrate with a via hole disposed through the dielectric substrate from a body fluid side to a device side. A conductive fill is disposed within the via forming a hermetic seal and is electrically conductive between the body fluid side and the device side. A feedthrough capacitor is attached to the dielectric substrate and includes a capacitor dielectric substrate, an unfilled capacitor via hole including an inner metallization, a set of capacitor active electrode plates electrically coupled to the inner metallization, an outer metallization disposed and a set of capacitor ground electrode plates electrically coupled to the outer metallization. A conductive leadwire is disposed within the unfilled capacitor via hole. An electrical joint connects the conductive fill, the capacitor inner metallization along with the capacitor active electrode plates and the conductive leadwire.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. patent application Ser. No.13/743,276, filed on Jan. 16, 2013, now U.S. Pat. No. 9,233,253, whichclaims priority from U.S. Pro. App. Ser. No. 61/587,029, filed on Jan.16, 2012; 61/587,287, filed on Jan. 17, 2012; and 61/587,373, filed onJan. 17, 2012.

FIELD OF THE INVENTION

The present invention generally relates to implantable medical devicesand hermetic terminal subassemblies. More particularly, the presentinvention relates to a hermetic terminal subassembly utilizing aco-fired essentially pure platinum filled via along with novel ways ofmaking electrical connections on the body fluid and device side of theactive implantable medical device (AIMD) housing.

BACKGROUND OF THE INVENTION

A wide assortment of active implantable medical devices (AIMD) arepresently known and in commercial use. Such devices include cardiacpacemakers, cardiac defibrillators, cardioverters, neurostimulators, andother devices for delivering and/or receiving electrical signals to/froma portion of the body. Sensing and/or stimulating leads extend from theassociated implantable medical device to a distal tip electrode orelectrodes in contact with body tissue.

The hermetic terminal or feedthrough of these implantable devices isconsidered critical. Hermetic terminals or feedthroughs are generallywell-known in the art for connecting electrical signals through thehousing or case of an AIMD. For example, in implantable medical devicessuch as cardiac pacemakers, implantable cardioverter defibrillators, andthe like, a hermetic terminal comprises one or more conductive terminalpins supported by an insulative structure for feedthrough passage fromthe exterior to the interior of an AIMD electromagnetic shield housing.Hermetic terminals or feedthroughs for AIMDs must be biocompatible aswell as resistant to degradation under applied bias current or voltage.Hermeticity of the feedthrough is imparted by judicious materialselection and carefully prescribed manufacturing processing. Sustainablehermeticity of the feedthrough over the lifetime of these implantabledevices is critical because the hermetic terminal intentionally isolatesthe internal circuitry and components of the device from the externalenvironment to which the component is exposed. In particular, thehermetic terminal isolates the internal circuitry, connections, powersources and other components in the device from ingress of body fluids.Ingress of body fluids into an implantable medical device is known to bea contributing factor to device malfunction and may contribute to thecompromise or failure of electrical circuitry, connections, powersources and other components within an implantable medical device thatare necessary for consistent and reliable device therapy delivery to apatient. Furthermore, ingress of body fluids may compromise animplantable medical device's functionality which may constituteelectrical shorting, element or joint corrosion, metal migration orother such harmful consequences affecting consistent and reliable devicetherapy delivery.

In addition to concerns relative to sustained terminal or feedthroughhermeticity, other potentially compromising conditions must beaddressed, particularly when a hermetic terminal or feedthrough isincorporated within an implantable medical device. For example, thehermetic terminal or feedthrough pins are typically connected to one ormore leadwires of implantable therapy delivery leads. These implantabletherapy delivery leads can effectively act as antennas ofelectromagnetic interference (EMI) signals. Therefore, when theseelectromagnetic signals enter within the interior space of a hermeticimplantable medical device, facilitated by the therapy delivery leads,they can negatively impact the intended function of the medical deviceand as a result, negatively impact therapy delivery intended for apatient by that device. EMI engineers commonly refer to this as the“genie in the bottle” effect. In other words, once the genie (i.e., EMI)is inside the hermetic device, it can wreak havoc with electroniccircuit functions by cross-coupling and re-radiating within the device.

Another particularly problematic condition associated with implantedtherapy delivery leads occurs when a patient is in an MRI environment.In this case, the electrical currents imposed on the implanted therapydelivery leads can cause the leads to heat to the point where tissuedamage is likely. Moreover, the electrical currents developed in theseimplanted therapy delivery leads during an MRI procedure can disrupt ordamage the sensitive electronics within the implantable medical device.

Therefore, materials selection and fabrication processing parameters areof utmost importance in creating a hermetic terminal (or feedthrough) ora structure embodying a hermetic terminal (or feedthrough), that cansurvive anticipated and possibly catastrophically damaging environmentalconditions and that can be practically and cost effectivelymanufactured.

Hermetic terminals or feedthrough assemblies utilizing ceramicdielectric materials may fail in a brittle manner. A brittle failuretypically occurs when the ceramic structure is deformed elastically upto an intolerable stress, at which point the ceramic failscatastrophically. Virtually all brittle failures occur by crackpropagation in a tensile stress field. Even microcracking caused bysufficiently high tensile stress concentrations may result in acatastrophic failure including loss of hermeticity identified ascritical in hermetic terminals for implantable medical devices. Loss ofhermeticity may be a result of design aspects such as a sharp cornerwhich creates a stress riser, mating materials with a difference ofcoefficient of thermal expansions (CTE) that generate tensile stressesthat ultimately result in loss of hermeticity of the feedthrough orinterconnect structure.

In the specific case of hermetic terminal or feedthrough designs, atensile stress limit for a given ceramic based hermetic design structurecannot be specified because failure stress in these structures is not aconstant. As indicated above, variables affecting stress levels includethe design itself, the materials selection, symmetry of the feedthrough,and the bonding characteristics of mating surfaces within thefeedthrough. Hence, length, width and height of the overall ceramicstructure matters as do the number, spacing, length and diameter of thevias in that structure. The selection of the mating materials, that is,the material that fills the vias and the material that forms the baseceramic, are important. Finally, the fabrication processing parameters,particularly at binder burnout, sintering and cool down, make adifference. When high reliability is required in an application such asindicated with hermetic terminals or feedthroughs for AIMDs, to provideensurance for a very low probability of failure it is necessary todesign a hermetic terminal assembly or feedthrough structure so thatstresses imparted by design, materials and/or processing are limited toa smaller level of an average possible failure stress. Further, toprovide ensurance for a very low probability of failure in a criticalceramic based assembly or subassembly having sustainable hermeticrequirements, it is also necessary to design structures embodying ahermetic terminal or feedthrough such that stresses in the finalassembly or subassembly are limited to a smaller level of an averagepossible failure stress for the entire assembly or subassembly. Inhermetic terminals and structures comprising hermetic terminals forAIMDs wherein the demand for biocompatibility exists, this task becomeseven more difficult.

The most critical feature of a feedthrough design or any terminalsubassembly is the metal/ceramic interface within the feedthrough thatestablishes the hermetic seal. The present invention therefore, providesa hermetic feedthrough comprising a monolithic alumina insulatorsubstrate within which a platinum conductive pathway or via resides.More specifically, the present invention provides a hermetic feedthroughin which the hermetic seal is created through the intimate bonding ofthe platinum metal residing within the alumina substrate.

A traditional ceramic-to-metal hermetic terminal is an assembly of threecomponents: metal leadwires that conduct electrical current, a ceramicinsulator, and a metal housing, which is referred to as the flange orthe ferrule. Brazed joints hermetically seal the metal leadwires and theflange or ferrule to the ceramic insulator. For a braze-bonded joint,the braze material is generally intended to deform in a ductile mannerin order to compensate for perturbations that stress the bond betweenthe mating materials as the braze material may provide ductile strainrelief when the thermal expansion mismatch between the ceramic and metalis large. Thus, mating materials with large mismatches in CTE can becoupled through braze materials whose high creep rate and low yieldstrength reduce the stresses generated by the differential contractionexisting between these mating materials.

Thermal expansion of metal is generally considerably greater than thoseof ceramics. Hence, successfully creating a hermetic structure, and onethat can sustain its hermeticity in service, is challenging due to thelevel of residual stresses in the final structure. Specifically, thermalexpansion mismatch results in stresses acting along the ceramic/metalinterface that tend to separate the ceramic from the metal and so thebond developed between the ceramic and the metal must be of sufficientstrength to withstand these stresses, otherwise adherence failure, thatis, loss of hermeticity, will occur. One method for limiting thesestresses is to select combinations of materials whose thermalcontractions after bonding are matched.

In making the selection for a CTE match, it is important to note thatvery few pairs of materials have essentially identical thermal expansioncurves. Generally, the metal component is selected first based onelectrical and thermal conductivity, thermal expansion, ability to bewelded or soldered, mechanical strength, and chemical resistance orbiocompatibility requirements; the ceramic is then selected basedprimarily on electrical resistivity, dielectric strength, low gaspermeability, environmental stability, and thermal expansioncharacteristics. In the specific case of selecting platinum wire, oftenthe ceramic formulation is modified in order to match its CTE to that ofthe platinum wire. In yet a more specific case of selecting platinumpaste, the platinum paste formulation may be modified as well. If themating materials are alumina of at least 96% purity and essentially pureplatinum paste, then matching CTE is not possible. Thus, for AIMD's,consistently achieving hermetic terminal structures that are capable ofsustaining hermeticity throughout the application's service life hasproven challenging.

Producing a stress-free structure often not only involves bonding a pairof materials but also achieving that bond at a very specific temperatureso that their contractions on cooling to room temperature areessentially the same even though the contraction curves may notcoincide. Since this often is a significant challenge, hermeticterminals are produced by metalizing the alumina and using a brazingmaterial to form the bond at some other temperature than an intersectionof the CTE curves. (NOTE: Forming a bond between two materials thatbecome rigid at the intersection of the two CTE curves makes it possibleto produce a structure that is stress free at room temperature, unlessthe two CTE curves separate substantially from each other from theintersection point and room temperature.) The deformation of the brazematerial by time-independent plastic flow or creep relaxation limits thestresses generated in the ceramic. Given this, the impact of the rate ofcooling on the final stress level of a structure must also beconsidered. In some cases, residual stresses are generated deliberatelyto provide protective compressive stresses in the ceramic part and inthe bond interface. Usually this is accomplished by selecting componentswith different CTEs. Another way is to control the shrinkage of onematerial over its mating material. In either case, it is important tominimize stress levels such that the interface on which hermeticitydepends is well within the stress level at which failure might occur.

In an embodiment, the present invention is directed to mating boundparticulate high purity alumina of at least 96% and particles ofessentially pure platinum metal that are suspended within a mixture ofsolvents and binders, i.e. a platinum paste. This combination ofmaterials does not use a braze material to buffer the CTE mismatchbetween these two materials. Further, since the intent of this inventionis to provide hermetic terminals and subassemblies comprising hermeticterminals for AIMDs, the present invention does not considermodifications to the alumina formulation or the platinum paste in anattempt to match their CTEs. Rather, this invention disclosessustainable hermetic terminals and structures embodying these hermeticterminals. This is achieved by adjusting platinum paste solids loading,prescribing via packing, prescribing binder burnout, sintering and cooldown parameters, such that shrinkage of the alumina is greater than theshrinkage of the platinum fill in the via and an intimate and tortuous(a mutually conformal) interface is created that may be either a directbond between the alumina and platinum materials that is hermetic.Alternatively, or that may develop an amorphous interfacial layer thatis not susceptible to erosion by body fluids and can tolerate stresslevels without losing hermeticity.

Regarding EMI, a terminal or feedthrough capacitor EMI filter may bedisposed at, near or within a hermetic terminal or feedthrough resultingin a feedthrough filter capacitor which diverts high frequencyelectrical signals from lead conductors to the housing or case of anAIMD. Many different insulator structures and related mounting methodsare known in the art for use of feedthrough capacitor EMI filters inAIMDs, wherein the insulative structure also provides a hermeticterminal or feedthrough to prevent entry of body fluids into the housingof an AIMD. In the prior art devices, the hermetic terminal subassemblyhas been combined in various ways with a ceramic feedthrough filter EMIcapacitor to decouple interference signals to the housing of the medicaldevice.

In a typical prior art unipolar construction (as described in U.S. Pat.No. 5,333,095 and herein incorporated by reference), a round/discoidal(or rectangular) ceramic feedthrough EMI filter capacitor is combinedwith a hermetic terminal pin assembly to suppress and decouple undesiredinterference or noise transmission along a terminal pin. The feedthroughcapacitor is coaxial having two sets of electrode plates embedded inspaced relation within an insulative dielectric substrate or base,formed typically as a ceramic monolithic structure. One set of theelectrode plates are electrically connected at an inner diametercylindrical surface of the coaxial capacitor structure to the conductiveterminal pin utilized to pass the desired electrical signal or signals.The other or second set of electrode plates are coupled at an outerdiameter surface of the round/discoidal capacitor to a cylindricalferrule of conductive material, wherein the ferrule is electricallyconnected in turn to the conductive housing of the electronic device.The number and dielectric thickness spacing of the electrode plate setsvaries in accordance with the capacitance value and the voltage ratingof the coaxial capacitor. The outer feedthrough capacitor electrodeplate sets (or “ground” plates) are coupled in parallel together by ametalized layer which is either fired, sputtered or plated onto theceramic capacitor. This metalized band, in turn, is coupled to theferrule by conductive adhesive, soldering, brazing, welding, or thelike. The inner feedthrough capacitor electrode plate sets (or “active”plates) are coupled in parallel together by a metalized layer which iseither glass frit fired or plated onto the ceramic capacitor. Thismetalized band, in turn, is mechanically and electrically coupled to thelead wire(s) by conductive adhesive, soldering, or the like. Inoperation, the coaxial capacitor permits passage of relatively lowfrequency biologic signals along the terminal pin, while shielding anddecoupling/attenuating undesired interference signals of typically highfrequency to the AIMD conductive housing. Feedthrough capacitors of thisgeneral type are available in unipolar (one), bipolar (two), tripolar(three), quadpolar (four), pentapolar (five), hexpolar (6) andadditional lead configurations. The feedthrough capacitors (in bothdiscoidal and rectangular configurations) of this general type arecommonly employed in implantable cardiac pacemakers and defibrillatorsand the like, wherein the pacemaker housing is constructed from abiocompatible metal such as titanium alloy, which is electrically andmechanically coupled to the ferrule of the hermetic terminal pinassembly which is in turn electrically coupled to the coaxialfeedthrough filter capacitor. As a result, the filter capacitor andterminal pin assembly prevents entrance of interference signals to theinterior of the pacemaker housing, wherein such interference signalscould otherwise adversely affect the desired cardiac pacing ordefibrillation function.

Regarding MRI related issues, bandstop filters, such as those describedin U.S. Pat. No. 6,008,980, which is herein incorporated by reference,reduce or eliminate the transmission of damaging frequencies along theleads while allowing the desired biologic frequencies to passefficiently through.

Referring once again to feedthrough capacitor EMI filter assemblies,although these assemblies as described earlier have performed in agenerally satisfactory manner, and notwithstanding that the associatedmanufacturing and assembly costs are unacceptably high in that thechoice of the dielectric material for the capacitor has significantimpacts on cost and final performance of the feedthrough filtercapacitor, alumina ceramic has not been used in the past as thedielectric material for AIMD feedthrough capacitors. Alumina ceramic isstructurally strong and biocompatible with body fluids but has adielectric constant around 6 (less than 10). There are other moreeffective dielectric materials available for use in feedthrough filtercapacitor designs. Relatively high dielectric constant materials (forexample, barium titanate with a dielectric constant of over 2,000) aretraditionally used to manufacture AIMD feedthrough capacitors forintegrated ceramic capacitors and hermetic seals resulting in moreeffective capacitor designs. Yet ceramic dielectric materials such asbarium titanate are not as strong as the alumina ceramic typically usedto manufacture the hermetic seal subassembly in the prior art. Bariumtitanate is also not biocompatible with body fluids. Direct assembly ofthe ceramic capacitor can result in intolerable stress levels to thecapacitor due to the mismatch in thermal coefficients of expansionbetween the titanium pacemaker housing (or other metallic structures)and the capacitor dielectric. Hence, particular care must be used toavoid cracking of the capacitor element. Accordingly, the use ofdielectric materials with a low dielectric constant and a relativelyhigh modulus of toughness are desirable yet still difficult to achievefor capacitance-efficient designs.

Therefore, it is very common in the prior art to construct a hermeticterminal subassembly with a feedthrough capacitor attached near theinside of the AIMD housing on the device side. The feedthrough capacitordoes not have to be made from biocompatible materials because it islocated on the device side inside the AIMD housing. The hermeticterminal subassembly allows leadwires to hermetically pass through theinsulator in non-conductive relation with the ferrule or the AIMDhousing. The leadwires also pass through the feedthrough capacitor tothe inside of the AIMD housing. These leadwires are typically continuousand must be biocompatible and non-toxic. Generally, these leadwires areconstructed of platinum or platinum-iridium, palladium orpalladium-iridium, niobium or the like. Platinum-iridium is an idealchoice because it is biocompatible, non-toxic and is also mechanicallyvery strong. The iridium is added to enhance material stiffness and toenable the hermetic terminal subassembly leadwire to sustain bendingstresses. An issue with the use of platinum for leadwires is thatplatinum has become extremely expensive and may be subject to prematurefracture under rigorous processing such as ultrasonic cleaning orapplication use/misuse, possibly unintentional damaging forces resultingfrom Twiddler's Syndrome.

Accordingly, what is needed is a filtered structure like a hermeticterminal or feedthrough, any subassembly made using same and anyfeedthrough filter EMI capacitor assembly which minimizes intolerablestress levels, allows use of preferred materials for AIMDS andeliminates high-priced, platinum, platinum-iridium or equivalent noblemetal hermetic terminal subassembly leadwires. Also, what is needed isan efficient, simple and robust way to connect the leadwires in a headerblock to the novel hermetic terminal subassembly. Correspondingly, it isalso needed to make a similar efficient, simple and robust electricalconnection between the electronics on the device side of the AIMD to thefeedthrough capacitor and hermetic terminal subassembly. The presentinvention fulfills these needs and provides other related advantages.

SUMMARY OF THE INVENTION

In an exemplary embodiment of the present invention, a co-firedhermetically sealed feedthrough may be attachable to an activeimplantable medical device. The feedthrough includes an aluminadielectric substrate comprising at least 96% alumina. A via hole isdisposed through the alumina dielectric substrate from a body fluid sideto a device side. A substantially closed pore, fritless andsubstantially pure platinum fill is disposed within the via hole forminga platinum filled via electrically conductive between the body fluidside and the device side. A hermetic seal exists between the platinumfill and the alumina dielectric substrate, wherein the hermetic sealminimizes damaging tensile stresses and, optimally, may comprise amutually conformal interface (or tortuous, intimate knitline) betweenthe alumina dielectric substrate and the platinum fill.

In another exemplary embodiment, the alumina dielectric substrate mayinclude at least 99% alumina. The platinum fill and the aluminadielectric substrate may form a knitline comprising a glass that is atleast about 60% silica.

In another exemplary embodiment, the hermetic seal may comprise a leakrate no greater than 1×10⁻⁷ standard cubic centimeters helium per second(std cc He/sec). Alternatively, the hermetic seal may comprise a leakrate no greater than 1×10⁻⁸ std cc He/sec. Alternatively, the hermeticseal may comprise a leak rate no greater than 1×10⁻⁹ std cc He/sec.Alternatively, the hermetic seal may comprise a leak rate no greaterthan 1×10⁻¹⁰ std cc He/sec. Alternatively, the hermetic seal maycomprise a leak rate no greater than 1×10⁻¹¹ std cc He/sec.Alternatively, the hermetic seal may comprise a leak rate no greaterthan 1×10⁻¹² std cc He/sec.

In another exemplary embodiment a shrink rate during an elevatedtemperature sintering of the alumina dielectric substrate in a greenstate may be greater than the shrink rate of the platinum fill in thegreen state.

In another exemplary embodiment the platinum filled via may comprise alarger cross sectional area at either a first via end exposed to thebody fluid side or a second via end exposed to the device side ascompared to a smaller cross sectional area of the platinum filled viabetween the first and second via ends.

In another exemplary embodiment an electrically conductive cap orprotrusion may be co-fired to the platinum fill on the body fluid side.The cap or protrusion may comprise a biocompatible material. The cap orprotrusion may comprise platinum or titanium.

In another exemplary embodiment an adhesion metallization may bedisposed on an outside circumferential surface of the alumina dielectricsubstrate. A wetting metallization may be disposed on the adhesionmetallization. A ferrule may be disposed around the alumina dielectricsubstrate. A braze may hermetically seal the alumina dielectricsubstrate to the ferrule. The braze may comprise gold. The hermetic sealbraze between the alumina dielectric substrate and the ferrule maycomprises a leak rate no greater than 1×10⁻⁷, 1×10⁻⁸, 1×10⁻⁹, 1×10⁻¹⁰,1×10⁻¹¹, or 1×10⁻¹² std cc He/sec. The ferrule may comprise titanium.The adhesion metallization may comprise titanium. The wettingmetallization comprises niobium or molybdenum.

In another exemplary embodiment the alumina dielectric substrate maycomprise a castellation recess disposed on the device side. A monolithicchip capacitor may be disposed within the castellation recess, themonolithic chip capacitor comprising an active electrode plate setdisposed parallel to a ground electrode plate set. The active electrodeplate set may be electrically coupled to the platinum fill by a firstcircuit trace disposed within the alumina dielectric substrate, andwherein the ground electrode plate set may be electrically coupled tothe adhesion metallization by a second circuit trace disposed within thealumina dielectric substrate.

In another exemplary embodiment a feedthrough capacitor may be attachedto the alumina dielectric substrate. An insulative washer may bedisposed between the alumina dielectric substrate and the feedthroughcapacitor. The feedthrough capacitor may comprises a second dielectricsubstrate, a conductive capacitor via hole disposed through the seconddielectric substrate, a set of active electrode plates disposed withinthe second dielectric substrate and electrically coupled to theconductive capacitor via hole, an outside feedthrough capacitormetallization disposed on an outside of the feedthrough capacitor, and aset of ground plates disposed within the second dielectric substrate andelectrically coupled to the outside feedthrough capacitor metallization.The outside feedthrough capacitor metallization may be electricallycoupled to a ferrule.

In another exemplary embodiment a ball grid solder joint or braze may bebetween the conductive capacitor via hole and the platinum fill. Theconductive capacitor via hole may be unfilled. A device side wire may bedisposed within the conductive capacitor via hole and electricallycoupled to the platinum fill and set of active electrode plates by theball grid solder joint or braze.

In another exemplary embodiment a grounded via hole may be disposedthrough the alumina dielectric substrate from the body fluid side to thedevice side including a substantially closed pore, fritless andsubstantially pure grounded platinum fill disposed within the groundedvia hole forming a platinum filled grounded via electrically conductivebetween the body fluid side and the device side. A set of feedthroughground plates may be disposed within the alumina dielectric substrateelectrically coupled to the grounded platinum fill and the ferrule andin non-conductive relation to the platinum filled via.

In another exemplary embodiment a feedthrough capacitor may be attachedto the alumina dielectric substrate. The feedthrough capacitor maycomprise a second dielectric substrate, a conductive capacitor via holedisposed through the second dielectric substrate, a set of activeelectrode plates disposed within the second dielectric substrate andelectrically coupled to the conductive capacitor via hole, a conductivegrounded via hole disposed through the second dielectric substrate, anda set of ground plates disposed within the second dielectric substrateand electrically coupled to the conductive grounded via hole.

In another exemplary embodiment the conductive capacitor via hole andconductive grounded via hole may be unfilled. The leadwire may beconnectable at a first end to an AIMD electronic circuit and at itssecond end disposed within and electrically coupled to the conductivecapacitor via hole. A ground leadwire may be connectable at a first endto an AIMD electronic circuit and at its second end disposed within andelectrically coupled to the conductive grounded via hole.

In another exemplary embodiment a hermetically sealed braze may bebetween the wetting metallization and an active implantable medicaldevice housing.

In another exemplary embodiment the via hole may comprise a plurality ofvia holes, the platinum fill may comprise a plurality of platinum fills,the grounded via hole may comprise a plurality of grounded via holes,and the grounded platinum fill may comprise a plurality of groundedplatinum fills. The plurality of via holes and plurality of platinumfills may comprise at least two cross sectional areas. The plurality ofgrounded via holes and plurality of grounded platinum fills may compriseat least two cross sectional areas.

In another exemplary embodiment a conductive leadwire may be disposedwithin the platinum fill on the body fluid side. The conductive leadwiremay comprise platinum, platinum-iridium, palladium, palladium-iridium,niobium or other like noble, biocompatible and biostable material. Theconductive leadwire and platinum fill may be co-fired.

In another exemplary embodiment a crimp post may be disposed within theplatinum fill on the body fluid side. A double-sided crimp post may bedisposed through the platinum fill comprising a first crimp post end onthe body fluid side and a second crimp post end on the device side.

In an exemplary embodiment of the present invention, a co-firedhermetically sealed feedthrough is attachable to an active implantablemedical device. An alumina dielectric substrate may comprise at least 96percent alumina. A staggerless (absent conductive catch pads forensuring uninterrupted electrical conductivity) via hole may be disposedthrough the alumina dielectric substrate from a body fluid side to adevice side. A substantially closed pore, fritless and substantiallypure platinum fill may be disposed within the via hole forming aplatinum filled via electrically conductive between the body fluid sideand the device side. A hermetic seal may be between the platinum filland the alumina dielectric substrate, wherein the hermetic seal isfundamentally matched or compressive (devoid of excessive tensilestresses) and may comprise a mutually conformal interface (or tortuous,intimate knitline) between the alumina dielectric substrate and theplatinum fill and wherein the hermetic seal comprises a leak rate nogreater than 1×10⁻⁷ std cc He/sec.

In an exemplary embodiment of the present invention, a co-firedhermetically sealed feedthrough is attachable to an active implantablemedical device. An alumina dielectric substrate comprises at least 96%alumina. A staggerless via hole is disposed through the aluminadielectric substrate from a body fluid side to a device side. Asubstantially closed pore, fritless and substantially pure platinum fillis disposed within the via hole forming a platinum filled viaelectrically conductive between the body fluid side and the device side.A first hermetic seal is between the platinum fill and the aluminadielectric substrate wherein the hermetic seal comprises a leak rate nogreater than 1×10-7 std cc He/sec. A staggerless grounded via hole isdisposed through the alumina dielectric substrate from the body fluidside to the device side. A substantially closed pore, fritless andsubstantially pure grounded platinum fill is disposed within thegrounded via hole forming a grounded platinum filled via electricallyconductive between the body fluid side and the device side. A secondhermetic seal is between the grounded platinum fill and the aluminadielectric substrate wherein the second hermetic seal comprises a leakrate no greater than 1×10-7 std cc He/sec. A plurality of groundedelectrode plates are electrically coupled to the grounded platinumfilled via and in non-conductive relation to the platinum filled via. Anouter metallization is disposed on alumina dielectric substrate andelectrically connected to the plurality of grounded electrode plates.

In an exemplary embodiment of the present invention, a method ofmanufacturing a hermetically sealed feedthrough includes forming adielectric substrate comprising at least 96% alumina, forming at leastone staggerless via hole through the dielectric substrate, filling theat least one via hole with a conductive fill, the conductive fillincluding a platinum powder and an inactive organic binder, solvent,and/or plasticizer, placing the dielectric substrate and conductive fillinto an air filled heating chamber and heating the assembly to amonolithic structure. The platinum fill and the dielectric substrate mayform a knitline comprising a glass that is at least about 60% silica.

In another exemplary embodiment, the forming of the alumina dielectricsubstrate may comprise laminating a plurality of alumina dielectricsheets. The forming of the alumina dielectric substrate may comprisepressing an alumina powder. A shrink rate during the heating of thealumina dielectric substrate in a green state may be greater than ashrink rate of the platinum fill in the green state.

In an exemplary embodiment of the present invention, a co-firedhermetically sealed feedthrough is attachable to an active implantablemedical device. An alumina dielectric substrate comprises at least 96%alumina substantially free of sintering additives and glasses. Aconductive metallization is disposed through the alumina dielectricsubstrate from a body fluid side to a device side, wherein themetallization comprises a substantially closed pore, fritless andsubstantially pure platinum fill. A hermetic seal is between theconductive metallization and the alumina dielectric substrate, whereinthe hermetic seal is fundamentally matched or compressive and maycomprise a mutually conformal interface (or tortuous, intimate knitline)between the alumina dielectric substrate and the metallization, thehermetic seal comprising a leak rate no greater than 1×10⁻⁷ std ccHe/sec. The knitline between the alumina dielectric substrate and themetallization may comprise a glass that is at least about 60% silica.

In an embodiment, a feedthrough capacitor may be attached to thedielectric substrate, the feedthrough capacitor comprising a capacitordielectric substrate, an unfilled via hole including an innermetallization, a set of active electrode plates electrically coupled tothe inner metallization, an outer metallization disposed on an outsideof the feedthrough capacitor, and a set of ground electrode plateselectrically coupled to the outer metallization. A conductive leadwireis disposed within the unfilled via hole. A solder joint is electricallyconnecting the conductive fill, the capacitor inner metallization, theset of active electrode plates and the leadwire.

In another exemplary embodiment a hermetic seal may be between the viahole and the conductive fill. The hermetic seal may comprise a leak rateno greater than 1×10⁻⁷ std cc He/sec. The dielectric substrate maycomprise at least 96% alumina. The conductive fill may comprise asubstantially closed pore and fritless platinum fill. The hermetic sealis fundamentally matched or compressive and may comprise a mutuallyconformal interface (or tortuous, intimate knitline) between the aluminadielectric substrate and the platinum fill. The platinum fill and thealumina dielectric substrate may form a knitline comprising a glass thatis at least about 60% silica.

In another exemplary embodiment the outer metallization may comprise anadhesion metallization disposed on an outside circumferential surface ofthe dielectric substrate. The outer metallization may comprise a wettingmetallization disposed on the adhesion metallization. A ferrule may bedisposed around the dielectric substrate. A gold braze may hermeticallyseal the dielectric substrate to the ferrule. The gold braze hermeticseal between the dielectric substrate and the ferrule may comprise aleak rate no greater than 1×10⁻⁷ std cc He/sec. An insulative washer maybe disposed between the dielectric substrate and the feedthroughcapacitor. The capacitor outer metallization may be electrically coupledto the ferrule. The via hole may comprise a staggered via hole.

In an exemplary embodiment of the present invention, a co-solderedhermetic feedthrough, feedthrough capacitor, and leadwire assemblycomprises a dielectric substrate. At least one via hole is disposedthrough the dielectric substrate from a body fluid side to a deviceside. A conductive fill is disposed within the at least one via holeforming a hermetic seal and electrically conductive between the bodyfluid side and the device side. At least one grounded via hole isdisposed through the dielectric substrate from the body fluid side tothe device side. A conductive grounded fill is disposed within the atleast one grounded via hole and electrically conductive between the bodyfluid side and the device side. A set of feedthrough ground plates areelectrically coupled to the conductive grounded fill and innon-conductive relation to the conductive fill. An internally groundedfeedthrough capacitor is attached to the dielectric substrate, thefeedthrough capacitor comprising a capacitor dielectric substrate, anunfilled via hole including a first inner metallization, a set of activeelectrode plates electrically coupled to the first inner metallization,an unfilled grounded via hole including a second inner metallization, aset of ground electrode plates electrically coupled to the second innermetallization. At least one conductive leadwire is disposed within theunfilled via hole of the feedthrough capacitor. At least one conductivegrounded leadwire is disposed within the unfilled grounded via hole ofthe feedthrough capacitor. A co-solder joint is electrically connectingthe conductive fill, the set of capacitor active electrode plates andthe at least one conductive leadwire. A second co-solder joint iselectrically connecting the conductive grounded fill, the set ofcapacitor ground electrode plates and the at least one conductive groundwire.

In another exemplary embodiment the first and second co-solder jointsmay be simultaneously formed. A first hermetic seal may be between theat least one via hole and the conductive fill. A second hermetic sealmay be between the at least one grounded via hole and the conductiveground fill. The first and second hermetic seals comprise a leak rate nogreater than 1×10⁻⁷, 1×10⁻⁸, 1×10⁻⁹, 1×10⁻¹⁰, 1×10⁻¹¹ or 1×10⁻¹² std ccHe/sec.

In another exemplary embodiment an adhesion metallization may bedisposed on an outside circumferential surface of the dielectricsubstrate. A wetting metallization may be disposed on the adhesionmetallization. A ferrule may be disposed around the dielectricsubstrate. A ferrule braze may be hermetically sealing the dielectricsubstrate to the ferrule. The hermetic seal of the ferrule braze maycomprise a leak rate no greater than 1×10⁻⁷ std cc He/sec. Thedielectric substrate may comprise at least 90% alumina up to at least99.999% alumina. In a preferred embodiment, the dielectric substrate maycomprise at least 92% alumina. In another preferred embodiment, thedielectric substrate may comprise at least 94% alumina. In yet anotherpreferred embodiment, the dielectric substrate may comprise at least 96%alumina.

In another exemplary embodiment the alumina dielectric substrate may besubstantially free of sintering additives and glasses. The conductivefill and conductive grounded fill may comprise a substantially closedpore and fritless platinum fill. The first and second hermetic seal eachare fundamentally matched or compressive and may comprise a mutuallyconformal interface (or tortuous, intimate knitline) between the aluminadielectric substrate and the platinum fills. The knitline may comprise aglass that is at least about 60% silica. A third hermetic seal may beformed between the wetting metallization and an active implantablemedical device housing.

In an exemplary embodiment of the present invention, an elevatedfeedthrough attachable to a top or a side of an active implantablemedical device comprises a conductive ferrule. A dielectric substrate isdefined as comprising a body fluid side and a device side disposedwithin the conductive ferrule and comprising a body fluid side elevatedportion generally raised above the conductive ferrule. At least one viahole is disposed through the dielectric substrate from the body fluidside to the device side. A conductive fill is disposed within the atleast one via hole and electrically conductive between the body fluidside and the device side. A leadwire connection feature is on the bodyfluid side electrically coupled to the conductive fill and disposedadjacent to the elevated portion of the dielectric substrate.

In another exemplary embodiment the leadwire connection feature maycomprise a wire bond pad. The wire bond pad may be substantiallyL-shaped. A conductive leadwire may be electrically coupled to theleadwire connection feature. The conductive leadwire may comprise around wire, an oval wire, a ribbon wire, a braided wire, a stranded wireor a coiled wire. The L-shape may comprise a curve. The wire bond padmay comprise a stamped and bent wire bond pad. A portion of the wirebond pad may be co-fired within the conductive fill. A braze preform maybe electrically coupling the leadwire connection feature to theconductive fill. A laser weld may be electrically coupling the leadwireconnection feature to the conductive fill. The elevated portion of thedielectric substrate may comprise at least one castellation recess andthe wire bond pad is at least partially disposed within the at least onecastellation recess. The leadwire connection feature may compriseleadwire insertion hole and a laser weld access hole. The leadwireconnection feature may comprise a leadwire insertion hole and a sideaccessed set screw. The at least one via hole may be partially unfilledand the leadwire connection feature may comprise an insertable contactspring configured to be located within the at least one partiallyunfilled via hole and electrically coupled to the conductive fill. Acircuit trace may be disposed within the dielectric substrateelectrically coupling the conductive fill and the leadwire connectionfeature. The at least one via hole may comprise at least one staggeredvia hole. A header block may be associated with the elevatedfeedthrough, wherein the header block comprises an access aperturecorresponding to a location adjacent to the leadwire connection feature.

In an exemplary embodiment of the present invention, an elevatedfeedthrough attachable to a top or a side of an active implantablemedical device comprises a conductive ferrule, a dielectric substratedefined as comprising a body fluid side and a device side disposedwithin the conductive ferrule and comprising a body fluid side elevatedportion generally raised above the conductive ferrule, at least one viahole disposed through the dielectric substrate from the body fluid sideto the device side, a conductive fill disposed within the at least onevia hole and electrically conductive between the body fluid side and thedevice side, at least one leadwire connection feature on the body fluidside electrically coupled to the conductive fill and disposed adjacentto the elevated portion of the dielectric substrate, and a header blockassociated with the elevated feedthrough, wherein the header blockcomprises an access aperture corresponding to a location adjacent to theleadwire connection feature.

In an exemplary embodiment of the present invention, an elevated wirebond pad feedthrough attachable to an active implantable medical devicecomprises a conductive ferrule, a dielectric substrate defined ascomprising a body fluid side and a device side disposed within theconductive ferrule, at least one via hole disposed through thedielectric substrate from the body fluid side to the device side, aconductive fill disposed within the at least one via hole andelectrically conductive between the body fluid side and the device side,a leadwire connection feature on the body fluid side electricallycoupled and co-fired within the conductive fill and protruding above thedielectric substrate comprising a side-accessible wire bond pad.

In another exemplary embodiment a support recess may be adjacent to andbehind the side-accessible wire bond pad configured to abut a support onan associated header block. A header block associated with thefeedthrough may comprises an access aperture corresponding to a locationadjacent to the side-accessible wire bond pad. A slot may be disposedwithin the side-accessible wire bond pad.

In an exemplary embodiment of the present invention an elevatedfeedthrough attachable to an active implantable medical device comprisesa conductive ferrule, a dielectric substrate defined as comprising abody fluid side and a device side disposed within the conductive ferruleand comprising an elevated portion generally raised above the conductiveferrule, at least one first metallization disposed through thedielectric substrate from the device side and stopping before exitingthe body fluid side, at least one leadwire connection feature on thebody fluid side electrically coupled to the at least one firstmetallization and disposed adjacent to the elevated portion of thedielectric substrate, and at least one circuit trace disposed within thedielectric substrate electrically connecting the at least one leadwireconnection feature and the at least one first metallization.

In another exemplary embodiment, the dielectric substrate may comprise asecond elevated portion generally raised above the elevated portion. Atleast one second metallization may be disposed through the dielectricsubstrate from the device side and stopping before exiting the bodyfluid side. At least one second leadwire connection feature on the bodyfluid side may be electrically coupled to the at least one secondmetallization and disposed adjacent to the second elevated portion ofthe dielectric substrate. At least one second circuit trace may bedisposed within the dielectric substrate electrically connecting the atleast one second leadwire connection feature and the at least one secondmetallization. The dielectric substrate may comprise a plurality ofraised elevated portions generally raised above the first and secondelevated portions.

In an exemplary embodiment of the present invention a header attachableto an active implantable medical device comprises a biocompatible headerblock, a leadwire disposed within the header, a leadwire portconnectable to an implantable lead and electrically coupled to theleadwire, and a feedthrough connection feature coupled to the leadwirecomprising a moveably biased electrical connector configured to abut ametallization of a hermetic feedthrough for the active implantablemedical device.

In another exemplary embodiment, the biased electrical connector maycomprise a compression spring biasing a moveable plunger, a cantileveredbeam or a flexure.

Other features and advantages of the present invention will becomeapparent from the following more detailed description, when taken inconjunction with the accompanying drawings, which illustrate, by way ofexample, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a wire-formed diagram of a generic human body showing a numberof exemplary implantable medical devices;

FIG. 2 is a side view of a prior art cardiac pacemaker;

FIG. 3 is a perspective view of a prior art cardiac pacemaker;

FIG. 3A is a perspective view of the prior art cardiac pacemaker of FIG.3 now showing placements of the leads into the heart;

FIG. 4 is a perspective view of a prior art feedthrough capacitor;

FIG. 5 is a sectional view of the prior art feedthrough capacitor ofFIG. 4 mounted to a hermetic terminal subassembly;

FIG. 6 is an electrical schematic diagram of the capacitor of FIG. 5;

FIG. 7 is a perspective view of the quad polar feedthrough capacitor andhermetic terminal assembly of FIG. 3;

FIG. 8 is a sectional view of the feedthrough and hermetic terminalassembly of FIG. 7;

FIG. 9 is a sectional view of a prior art hermetic insulator with asolid metallic filled via in a green state;

FIG. 10 is a sectional view of the structure of FIG. 9 now aftersintering;

FIG. 10A is an enlarged view taken from FIG. 10 along lines 10A-10A nowshowing gaps between the solid metallic leadwire and the insulator;

FIG. 11 is a sectional view of a prior art hermetic insulator with ametallic paste filled via;

FIG. 11A is an enlarged view of the structure of FIG. 11 now showingirregular glass filled structures;

FIG. 12 is a flow chart illustrating the main steps of one embodiment ofthe process of the present invention;

FIG. 13 is a sectional view of a hermetic terminal assembly of thepresent invention comprising a high purity alumina ceramic and a pureplatinum filled via hole in a green state;

FIG. 14 is another sectional view of a hermetic terminal assembly of thepresent invention now showing stacking build up from individual tapelayers in a green state;

FIG. 15 is a sectional view of the hermetic terminal assembly of FIGS.13-14 after a co-firing process;

FIG. 16 is an enlarged view of the structure of FIG. 15 now showing amutually conformal interface (or tortuous, intimate knitline);

FIG. 17 is a sectional view of an embodiment of a novel hermeticterminal subassembly of the present invention installed in an housing ofan AIMD;

FIG. 17A is a sectional view similar to FIG. 17 showing individual tapelayers comprising the insulator;

FIG. 17B is a sectional view similar to FIGS. 17 and 17A now showing theplatinum filled via with a smaller diameter center section as comparedto the ends of the platinum filled via;

FIG. 18 is a sectional view similar to FIGS. 17, 17A and 17B now showinga wire bond cap co-fired into the platinum filled via;

FIG. 19A is a top view of an exemplary embodiment of a hermetic terminalsubassembly now showing a plurality of filled vias;

FIG. 19B is a sectional view taken from lines 19B-19B of FIG. 19A nowshowing a neuro-electrode co-fired into the platinum filled via;

FIG. 19C is a top view of a prior art quad polar hermetic feedthrough;

FIG. 19D is a top view of the novel hermetic terminal subassemblyshowing the increased number of leadwires possible as compared to FIG.19C;

FIG. 20 is a sectional view of an exemplary embodiment of a hermeticterminal subassembly of the present invention now showing castellationswith MLCCs;

FIG. 21 is a sectional view taken from FIG. 20 along lines 21-21 nowshowing internal circuit traces;

FIG. 22 is a sectional view of an exemplary embodiment of a hermeticterminal subassembly now showing a capacitor with a filled and abore-coated via;

FIG. 22A is a sectional view similar to the structure of FIG. 22 nowshowing an exemplary embodiment without a ferrule where the insulator isattached to the AIMD housing;

FIG. 23 is a sectional view of an exemplary embodiment of a hermeticterminal subassembly now showing a capacitor with an internal ground andan insulator with ground plates;

FIG. 23A is a sectional view similar to the structure of FIG. 23 nowshowing an exemplary embodiment without a ferrule where the insulator isattached to the AIMD housing;

FIG. 24 is a sectional view of the ground plate of FIG. 23 taken alonglines 24-24;

FIG. 25 is a sectional view of the ground plate of FIG. 23 taken alonglines 25-25 now showing a ten leadwire configuration;

FIG. 26 is a sectional view similar to FIGS. 24-25 now showing extraground vias to improve EMI filter attenuation;

FIG. 27 is a perspective view of a prior art header block connectorassembly;

FIG. 28 is a side view of an exemplary embodiment of a novel side windowin a header block of an AIMD;

FIG. 29 is a perspective and enlarged view of a hermetic terminalassembly with various novel side attachment configurations accessiblethrough the novel header block side window;

FIG. 29A is a perspective view of a paddle lead;

FIG. 29B is a perspective view of a ribbon lead;

FIG. 30 is a sectional view taken from the structure of FIG. 29 alonglines 30-30;

FIG. 31 is an enlarged view taken from FIG. 30 along lines 31-31;

FIG. 32 is a sectional view of another exemplary embodiment similar toFIG. 30 now showing a gold braze perform connecting the side mountedwire bond pad and the platinum fill;

FIG. 33 is a sectional view similar to FIG. 32 now showing a curvedradius insulator;

FIG. 34 is a sectional view similar to FIG. 33 now showing a three-wayconnection between the internal AIMD leadwires, the capacitor activeplates through the bore-coated metallization and the platinum fill ofthe insulator;

FIG. 35 is a sectional view similar to FIG. 30 now showing anotherexemplary embodiment of the present invention;

FIG. 36 is a sectional view taken from FIG. 35 along lines 36-36 nowshowing the active plates;

FIG. 37 is a sectional view taken from FIG. 35 along lines 37-37 nowshowing the ground plates;

FIG. 38 is a perspective view of an exemplary embodiment of a round quadpolar hermetic terminal assembly;

FIG. 39 is a perspective view of an exemplary wire bond pad;

FIG. 40 is a perspective view of another exemplary wire bond pad;

FIG. 41 is a perspective view of another exemplary wire bond pad;

FIG. 42 is a perspective view of another exemplary wire bond pad;

FIG. 43 is a perspective view of an exemplary embodiment of a hermeticterminal subassembly now showing castellations formed in the insulatorconfigured to receive wire bond pads;

FIG. 44 is a perspective view of another exemplary embodiment of ahermetic terminal subassembly similar to FIG. 43 now showing deepercastellations;

FIG. 45 is a perspective view of another exemplary embodiment of ahermetic terminal subassembly now showing leadwire holes and set screws;

FIG. 46 is a perspective view of another exemplary embodiment of ahermetic terminal subassembly now showing an insertable contact spring;

FIG. 47 is a sectional view of the structure of FIG. 46 taken alonglines 47-47;

FIG. 48 is an enlarged view of the structure of FIG. 47 taken alonglines 48-48;

FIG. 49 is a perspective view of another exemplary embodiment of ahermetic terminal subassembly now showing laser weld access holes;

FIG. 50 is a perspective view of an embodiment of a wire bond pad;

FIG. 50A is a perspective view of an embodiment of wire bond pad similarto FIG. 50;

FIG. 51 is a sectional view of the structure of FIG. 50A taken alonglines 51-51;

FIG. 52 is an enlarged sectional view of the wire bond pad of FIGS. 50Aand 51 co-fired into the platinum filled via;

FIG. 53 is a perspective view of another embodiment of a wire bond padwith attachment fingers;

FIG. 53A is a perspective view of the embodiment of wire bond padsimilar to FIG. 53;

FIG. 54 is an enlarged sectional view of another embodiment of a wirebond pad with a pin co-fired into the platinum filled via;

FIG. 55 is an enlarged sectional view of another embodiment of a wirebond pad similar to FIG. 55 now showing a hole to capture the leadwire;

FIG. 56 is an enlarged sectional view of another embodiment of a wirebond pad similar to FIGS. 55 and 56 now showing a gold braze;

FIG. 57 is a perspective view of another embodiment of a hermeticterminal subassembly with internal circuit traces;

FIG. 58 is an enlarged sectional view taken from FIG. 57 along lines58-58 showing the internal circuit traces;

FIG. 59 is a sectional view taken from FIG. 57 along lines 59-59;

FIG. 60 is a sectional view of another exemplary embodiment of ahermetic terminal subassembly now showing a solid wire co-fired into theplatinum filled via;

FIG. 61 is a sectional view of an embodiment of a filled via withinternal circuit traces;

FIG. 62 is a sectional view similar to FIG. 59 now showing a staggeredvia hole;

FIG. 63 is a sectional view similar to FIG. 62 now showing a staggeredvia hole with a solid wire co-fired into the platinum filled via;

FIG. 64 is a sectional view of an exemplary embodiment of a crimp postco-fired into the platinum filled via;

FIG. 65 is a sectional view of an exemplary embodiment of a double crimppost co-fired into the platinum filled via;

FIG. 66 is a perspective view of an exemplary embodiment of a novelmethod of header block connector assembly attachment showing a supportstructure behind the wire bond pads;

FIG. 67 is a perspective view of a wire bond pad of FIG. 66 with a novelslot;

FIG. 68 is a perspective view of an exemplary embodiment of a hermeticterminal subassembly now showing a high density stacking configuration;

FIG. 69 is a sectional view taken from the structure of FIG. 69 alonglines 69-69;

FIG. 70 is a perspective view of another exemplary embodiment of ahermetic terminal subassembly now showing an alternative high densitystacking configuration;

FIG. 71 is a perspective view of another exemplary embodiment of ahermetic terminal subassembly now showing an alternative high densitystacking configuration;

FIG. 72 is a perspective view of an AIMD and header block with a windowallowing access to connect the side attachment wire bond pads to theleadwires;

FIG. 73 is a sectional view with a novel crimp post co-fired into theplatinum filled via;

FIG. 74 is a perspective view of another exemplary embodiment of a novelcrimp post similar to FIG. 73;

FIG. 75 is a perspective view of another exemplary embodiment of a novelcrimp post similar to FIG. 73;

FIG. 76 is a perspective view of another exemplary embodiment of a novelcrimp post similar to FIG. 73;

FIG. 77 is a perspective view of another exemplary embodiment of a novelcrimp post similar to FIG. 73;

FIG. 78 is a perspective view of another exemplary embodiment of a novelcrimp post similar to FIG. 73;

FIG. 79 is a sectional view of an exemplary embodiment of a novel springelectrically connecting the platinum filled via to the leadwires in theheader block;

FIG. 80 is a sectional view of another exemplary embodiment of leadwireattachment to the platinum filled vias;

FIG. 81 is a sectional view rotated 90° taken from FIG. 80 along lines81-81;

FIG. 82 is a side perspective view of another exemplary embodiment of anovel spring electrically connecting the platinum filled via to theleadwires in the header block; and

FIG. 83 is a side perspective view of another exemplary embodiment of anovel connector electrically connecting the platinum filled via to theleadwires in the header block.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates various types of active implantable and externalmedical devices 100 that are currently in use. FIG. 1 is a wire formeddiagram of a generic human body showing a number of implanted medicaldevices. 100A is a family of external and implantable hearing deviceswhich can include the group of hearing aids, cochlear implants,piezoelectric sound bridge transducers and the like. 100B includes anentire variety of neurostimulators and brain stimulators.Neurostimulators are used to stimulate the Vagus nerve, for example, totreat epilepsy, obesity and depression. Brain stimulators are similar toa pacemaker-like device and include electrodes implanted deep into thebrain for sensing the onset of a seizure and also providing electricalstimulation to brain tissue to prevent the seizure from actuallyhappening. The lead wires that come from a deep brain stimulator areoften placed using real time imaging. Most commonly such lead wires areplaced during real time MRI. 100C shows a cardiac pacemaker which iswell-known in the art. 100D includes the family of left ventricularassist devices (LVAD's), and artificial hearts, including the recentlyintroduced artificial heart known as the Abiocor. 100E includes anentire family of drug pumps which can be used for dispensing of insulin,chemotherapy drugs, pain medications and the like. Insulin pumps areevolving from passive devices to ones that have sensors and closed loopsystems. That is, real time monitoring of blood sugar levels will occur.These devices tend to be more sensitive to EMI than passive pumps thathave no sense circuitry or externally implanted lead wires. 100Fincludes a variety of external or implantable bone growth stimulatorsfor rapid healing of fractures. 100G includes urinary incontinencedevices. 100H includes the family of pain relief spinal cord stimulatorsand anti-tremor stimulators. 100H also includes an entire family ofother types of neurostimulators used to block pain. 100I includes afamily of implantable cardioverter defibrillators (ICD) devices and alsoincludes the family of congestive heart failure devices (CHF). This isalso known in the art as cardio resynchronization therapy devices,otherwise known as CRT devices. 100J illustrates an externally wornpack. This pack could be an external insulin pump, an external drugpump, an external neurostimulator, a Holter monitor with skin electrodesor even a ventricular assist device power pack. 100K illustrates theinsertion of an external probe or catheter. These probes can be insertedinto the femoral artery, for example, or in any other number oflocations in the human body.

FIG. 2 illustrates a prior art cardiac pacemaker 100C showing a sideview. The pacemaker electronics are housed in a hermetically sealed andconductive electromagnetic shield 102 (typically titanium). There is aheader block assembly 104 generally made of thermal-settingnon-conductive plastic, such as Techothane. This header block assembly104 houses one or more connector assemblies generally in accordance withISO Standards IS-1, IS-2, or more modern standards, such as IS4 or DF4.These header block connector port assemblies are shown as 106 and 106′.Implantable leadwires (not shown) have proximal plugs and are designedto insert into and mate with these header block connector cavities 106and 106′, or, in devices that do not have header block assemblies, incavities built directly into the pulse generator itself.

As used herein, the term “lead” refers to an implantable lead containinga lead body and one or more internal lead conductors. A “lead conductor”refers to the conductor that is inside of an implanted lead body. Asused herein, the term “leadwire” refers to wiring that is either insideof the active implantable medical device (AIMD) housing or inside of theAIMD header block assembly or both. As used herein, the term headerblock is the biocompatible material that attaches between the AIMDhousing and the lead. The term header block connector assembly refers tothe header block including the connector ports for the leads and thewiring connecting the lead connector ports to the hermetic terminalsubassemblies which allow electrical connections to hermetically passinside the device housing. It is also understood by those skilled in theart that the present invention can be applicable to active implantablemedical devices that do not have a header block or header blockconnector assemblies such as pulse generators.

FIG. 3 is a prior art cardiac pacemaker 100C similar to that previouslyillustrated in FIG. 2 except that additional interior and exteriordetails are illustrated. Referring to FIG. 3, one can see implantableleads 110 and 110′ which may have one or more internal lead conductors(not shown). In the present case, these are bipolar leads, meaning thateach lead 110 and 110′ has two internal lead conductors. One of theselead conductors is connected to a tip electrode 112 or 112′. The secondlead conductor is mounted to a ring electrode 113 or 113′ asillustrated. For a typical dual chamber bipolar cardiac pacemaker, onebipolar electrode will be placed into the right ventricle and the otherbipolar electrode will be placed into the right atrium of the humanheart 114. For example, tip electrode 112′ could be placed in the rightventricular apex and 113′ would be a bipolar electrode placed adjacentto the tip electrode 112′. In a similar manner, tip electrode 112 couldbe placed in the right atrial apex and ring electrode 113 would beplaced adjacent to the distal electrode 112 to provide bipolar sensingin the right atrium of the heart 114. The proximal ends of the leadsterminate in proximal connector plugs 108 and 108′. These proximalconnector plugs are designed to be inserted into connector cavities 106and 106′ of the cardiac pacemaker 100C header block assembly 104 or, fordevices without header block assemblies (not shown), into connectorcavities within the pulse generator itself. The proximal connectors arefirmly held in place in the connector cavities with set screws and thelike (also not shown). In this embodiment, the connector cavities 106and 106′ are in the header block assembly 104 and have a total of fourleadwires (118 a through 118 d) associated with them. These leadwiresare routed through a hermetic terminal subassembly 116. Each of the fourleadwires is routed from the body fluid side (the header block connectorassembly 104) to the inside of the cardiac pacemaker (inside thehermetically sealed container 102) by passing through the hermeticterminal subassembly 116. Each of the leadwires 118 pass through aferrule 122 of the hermetic terminal subassembly 116 in non-conductiverelationship. The non-conductive relationship is imparted by a singleinsulator 120 between each of the four leadwires 118 placed in the viasof the insulator 120. It is understood by those skilled in the art thatthe four hermetically sealed leadwires 118 could be replaced by a singlehermetically sealed leadwire comprising four individual conductors or byfour separate leadwires 118 each with their own insulator and ferruleassembly. Furthermore, those skilled in the art will appreciate that ahermetic terminal subassembly may be constructed with any number ofhermetically sealed leadwires in one or more large insulators having oneor more vias.

The ferrule 122 of the hermetic terminal subassembly 116 is generallymechanically and hermetically attached to the AIMD housing 102 by laserwelding 128 processes or the like. Attached directly on or adjacent tothe hermetic terminal subassembly 116 is a feedthrough capacitor 124which is used to decouple unwanted electromagnetic interference (EMI)signals that may couple to the implanted leads 110 and 110′. Thefeedthrough capacitor filter prevents such undesirable EMI signals fromentering into the interior of the pacemaker housing 102. It isparticularly adverse for high frequency EMI signals to enter into theinside of the AIMD housing 102 because once high frequency noise isinside, it can cross-couple or re-radiate to sensitive pacemakercircuits thereby disrupting proper operation of the device. For example,it has been documented in numerous technical papers that EMI can befalsely interpreted by a cardiac pacemaker as a normal heartbeat. Modernpacemakers are demand-type devices to save battery energy. That is, inthe presence of a normal heartbeat, they will turn off to save batteryenergy. If EMI is improperly sensed as a cardiac signal, and the deviceturns off (inhibits) this becomes immediately life-threatening to apacemaker dependent patient as, in this particular case, the patient'sheart will not function without the pacemaker. In this particular case,the patient's heart stops beating altogether because the pacemaker hasstopped providing the electrical pulses the heart needs to pump bloodand sustain life. Once the leadwires 118 a, 118 b, 118 c and 118 d passthrough the feedthrough capacitor, the high frequency electromagneticnoise has been largely eliminated and therefore the signals coming tothe circuit board 126 will be relatively clean and be comprisedprimarily of low frequency biologic signals and/or pacing pulses.

FIG. 3A is the same dual chamber cardiac pacemaker system previouslyillustrated in FIG. 3. It shows the detail of the placement of a distaltip electrode 112 into the right ventricular apex and its associatedring electrode 113. Also illustrated is the placement of a distal tipelectrode 112 into the right atrial apex along with its associated ringelectrode 113.

FIG. 4 illustrates a prior art feedthrough capacitor 124 similar to thequad polar feedthrough capacitor 124 previously illustrated in FIG. 3.However, in FIG. 4, the feedthrough capacitor is unipolar for simplicityin describing its construction. In the prior art, these feedthroughcapacitors are known as multilayer monolithic ceramic feedthroughcapacitors. They are three-terminal devices as opposed to simplemultilayer chip capacitors (MLCC), which are two-terminal devices.Two-terminal devices have considerable internal inductance andself-resonate before they reach high frequencies. For this reason, theydo not make very effective broadband EMI filters. In contrast, thethree-terminal devices, also known as feedthrough capacitors, areexceptional broadband devices that work from the low kilohertz frequencyrange through to and beyond 10 GHz. Referring once again to FIG. 4, onecan see that there are alternating stacks of active electrodes 134interspersed with ground electrodes 136. These are all fired in adielectric medium 154. In general, feedthrough capacitor dielectrics areof barium titanate, strontium titanate or the like. This makes for ahighly volumetrically efficient capacitor since these dielectricconstants are, in general, 100 to 5000 times more efficient than an aircapacitor. In order to make contact with all of the ground electrodeplates 136, an exterior metallization 132 is applied. This can be aplated metallization or it could be a silver or palladium silver glassfrit which forms the metallization layer when fired at elevatedtemperature. This has the effect of placing all the ground electrodeplates 136 in parallel and also provides a surface on which to make aconvenient electrical connection to the ground electrode plates. Thereis a similar metallization 130 that is applied to the inside diameterhole of feedthrough capacitor 124. This inside diameter metallization130 makes contact with the active electrode plate set 134.

FIG. 5 is a cross-sectional view of the unipolar capacitor of FIG. 4shown mounted to a hermetic terminal subassembly 116 which is, in turn,installed into the metallic housing 102 of an AIMD 100. In FIG. 5, theinternal active electrode plate set 134 and ground electrode plate set136 are visible. In this case, there is a leadwire 118 which passes allthe way through a hermetic insulator 120 and also through the centerhole of the feedthrough capacitor 124. The hermetic leadwire insulator120 is shown which is typical of alumina ceramic, glass or other similarinsulative material. In this example, the leadwire 118 is gold brazed138 to the alumina ceramic insulator 120. The alumina ceramic insulator120 is of ceramic material and requires metallization for wetting of thegold braze and ultimately hermetically sealing to the ceramic.Accordingly, it is important that surface preparations such asmetallization be completed prior to the gold brazing operation. Layer152 is a sputtered adhesion layer typically titanium. Sputtered overthis is a wetting layer 150 which would typically be of molybdenum,niobium or the like, to which a gold braze will readily wet and form ahermetic seal. Both the outside diameter and the inside diameter of thehermetic insulator 120 is thus metalized in preparation for gold brazingoperation. A similar gold braze 140 is formed between the outsidediameter of the hermetic seal insulator 120 and the ferrule 122.Sputtered layers for fabricating hermetic terminal assemblies 116 couldbe metals other than the typical titanium, niobium and molybdenumexamples provided herein.

The feedthrough capacitor 124 is generally bonded at or adjacent to thehermetic terminal assembly 116. The reason for this is it is veryimportant to intercept and decouple electromagnetic signals before theycan enter into the interior space of the AIMD housing. EMI engineerscall this the “genie in the bottle” effect. In other words, once thegenie (i.e., EMI) is inside the AIMD housing 102, it can wreak havocwith electronic circuit functions by cross-coupling and re-radiating allover and anywhere within the bottle (i.e., the pulse generator).Consequently, it is very important that the feedthrough capacitor filterelement be disposed at the point of leadwire ingress/egress where it canattenuate and/or filter high frequency electromagnetic noise before itbecomes detrimental to the intended therapy delivery of the AIMD, andpotentially life threatening to the patient. Accordingly, thefeedthrough capacitor 124 has an electrical connection 146 between thecapacitor electrode plate metallization 130 and terminal pin 118. Thereis a similar electrical connection 148 made between the capacitoroutside diameter metallization 132 and the ferrule 122 of the hermeticseal housing. In this particular connection, an added performancereliability benefit is realized. In general, making an electricalconnection 148 directly to a titanium surface is contraindicated. Thisis because titanium forms oxides which tend to be resistive,particularly at high frequency. By way of the present invention,connection is always made to a non-oxidized surface, such as the goldbraze or a gold bond pad 140. In the case of the latter, one is referredto U.S. Pat. No. 6,765,779, which illustrates such gold bond padconnections, the contents of which are herein incorporated by reference.The ferrule 122 of the hermetic terminal subassembly is generally laserwelded 128 to the titanium housing 102 of the AIMD. The housing 102forms a complete and hermetically sealed chamber, but also forms anoverall electromagnetic shield. This is also known as an equipotentialsurface or ground. The ground symbol 144 illustrated in FIG. 5represents that this is indeed a shielded equipotential surface.

FIG. 6 is a schematic diagram taken from FIG. 5 illustrating theunipolar feedthrough capacitor 144. This is known in the industry as athree-terminal device. It has an end disposed toward body fluids 118 andthen the leadwire passes through the feedthrough capacitor electrodeplates to the interior of the AIMD at location 118′. The capacitorground electrode plates are electrically grounded to the AIMD housing102, 144. This yields three distinct terminal locations 118, 118′ and144. Substantial signal attenuation occurs at high frequency from theterminal one end of the leadwire 118 to the terminal two end of theleadwire at 118′. In this way leadwire terminal ends one 118 and two118″ along with the ground 144 form a feedthrough capacitor known in theart as a three-terminal device.

FIG. 7 illustrates the quad polar feedthrough capacitor and hermeticterminal subassembly 116 previously illustrated in FIG. 3. It is verysimilar to the unipolar capacitor illustrated in FIGS. 4, 5 and 6 exceptin this case it has four leadwires 118 a-118 d and four feedthroughholes (quad polar). It has a metallic ferrule 122 generally of titaniumwhich is ready for laser welding into the AIMD housing 102 (not shown).

FIG. 8 is a prior art sectional view taken generally from section 8-8from FIG. 7. This illustrates the hermetic terminal subassemblyleadwires 118 a-d passing through the hermetic terminal subassemblyinsulator 120 in non-conductive relationship and also through thefeedthrough capacitor 124 wherein the active electrode plates 134 areelectrically connected 146 to the hermetic terminal subassembly leadwire118 and wherein the feedthrough capacitor ground electrode plates 136are electrically connected 148 to the hermetic terminal subassemblyferrule 122 and gold braze 140. Referring once again to FIGS. 3, 5, 7and 8, in each case it is seen that the hermetic terminal subassemblyleadwires 118 a-d pass all the way through the entire structure, namely,the hermetic terminal subassembly 116 and the feedthrough capacitor 124.In general, these hermetic terminal subassembly leadwires 118 a-d arecontinuous and pass through from the body fluid side to the inside ofthe device 100 housing 102. Because the hermetic terminal subassemblyleadwires 118 a-d pass through from the body fluid side to the inside ofthe device by way of header block connector assembly or the like, it isvery important that these hermetic terminal subassembly leadwire 118materials be both biocompatible and non-toxic. Generally in the priorart, these hermetic terminal subassembly leadwires are constructed ofplatinum or platinum-iridium, palladium or palladium-iridium, niobium orthe like. Platinum-iridium is an ideal choice because it isbiocompatible, non-toxic and is also mechanically very strong. Theiridium is added to enhance material stiffness and to enable thehermetic terminal subassembly leadwire to sustain bending stresses.

An issue with the use of platinum for hermetic terminal subassemblyleadwires 118 a-d is that platinum has become extremely expensive andmay be subject to premature fracture under rigorous processing such asultrasonic cleaning or application use/misuse, possibly unintentionaldamaging forces resulting from Twiddler's Syndrome. Accordingly, what isneeded is a filtered structure like a feedthrough-feedthrough capacitorassembly 116, 124 which eliminates these high-priced, platinum,platinum-iridium or equivalent noble metal hermetic terminal subassemblyleadwires 118. For additional examples of hermetic terminalsubassemblies with feedthrough capacitors that employ leadwires 118, oneis referred to U.S. Pat. Nos. 5,333,095, 5,896,267, 5,751,539,5,905,627, 5,959,829, 5,973,906, 6,008,980, 6,159,560, 6,275,379,6,456,481, 6,529,103, 6,566,978, 6,567,259, 6,643,903, 6,765,779,6,765,780, 6,888,715, 6,985,347, 6,987,660, 6,999,818, 7,012,192,7,035,076, 7,038,900, 7,113,387, 7,136,273, 7,199,995. 7,310,216,7,327,553, 7,489,495, 7,535,693, 7,551,963, 7,623,335, 7,797,048,7,957,806, 8,095,224, 8,179,658 the contents of all of which areincorporated herein by reference.

As discussed earlier, for ceramic based hermetic terminals orfeedthroughs, the most critical feature in its design is themetal/ceramic interface. Also as indicated above, one method forlimiting residual stress is to select combinations of materials whosethermal contractions after bonding are matched. Alternatively, materialswith different CTEs can be coupled through braze materials whose highcreep rate and low yield strength reduce the stresses generated by thedifferential contraction. Given the challenge associated with CTEmatching, it is the intent of the present invention to deliberatelygenerate hermetic structures with residual stress levels such thateither matched hermetic structures or structures that have protectivelycompressive stresses from the ceramic part to the filled via material atthe bonding interface are created, thereby creating a hermetic seal. Asgiven above, usually this is accomplished by selecting components withdifferent CTEs, however, the intent of the present invention is todeliberately create the desired level of residual stresses byjudiciously selecting the ceramic and via fill materials and prescribinga firing process that results in the ceramic material shrinking morethan that of the via fill material. Additionally, the intent of thepresent invention is to deliberately create a mutually conformalinterface (tortuous, intimate knitline) between the ceramic and the viafill materials. Further, the intent of the present invention is to alsodeliberately create an interface bond between the ceramic and the viafill material that is tolerant of stress and of CTE mismatch between theceramic and the via fill materials and is not susceptible to erosion bybody fluids so as to achieve sustainable hermeticity over service life.The term “knitline” is defined herein as the interfacial boundarybetween the alumina and the platinum. The knitline may form a meanderingor undulating path that provides sufficient tortuousity such that itinhibits crack initiation, and more importantly, crack propagation, andadditionally, because of the intimacy of the knitline, impairs leakageof fluids. As used herein, the word tortuous or tortuousity refers tothe roughened, complex, or undulating knitline that is formed at theinterfacial boundary between the alumina and the platinum. This tortuousinterface is characterized by hills and valleys which is topographicallythree dimensional and forms a very strong and reliable hermetic bond.

In part, the critical aspect of the metal/ceramic interface is relatedto the intimacy and tortuousity of the knitline formed when the metalsurface mates with the ceramic surface (i.e., post sintering, the metalsurface should mirror the image of the ceramic surface and intimately,or tightly, mate with each other), the type of bond between the ceramicand the metal (certain glass phased interfaces are contraindicated dueto their susceptibility to erosion by body fluids, and hence, subsequentseparation and loss of hermeticity at these interfaces), and thesensitivity of the bond strength to a tensile stress field (residualstresses in the final structure should be sufficiently less than thepossible failure stresses of the structure). Any broken symmetry,aberrant dimensionality due to poor process control, unfavorable designaspect ratios, design aspects wherein intolerable stress concentrationsor fields develop, atomic relaxation is inhibited and intermixing ofatoms at their boundaries that can substantially negatively modify thedeformational tolerance of the final structure must be considered whencreating interfaces between ceramic oxides and conductive metal viaswithin those ceramic oxides to preserve intentional immediate andsustainable functional behavior such as hermeticity.

There are a number of patents that disclose alternatives for platinumleadwires 118 in hermetic terminal subassemblies. Among these are a fewthat discuss hermetic terminals manufactured by a co-fire process andbased on an alumina ceramic with platinum paste filled vias. Some of themore prominent concepts are disclosed in U.S. Pat. No. 5,782,891 toHassler et al., U.S. Pat. No. 6,146,743 to Haq et al., U.S. Pat. No.6,414,835 to Wolf et al., U.S. Pat. No. 8,000,804 to Wessendorf et al.,U.S. Pat. No. 8,043,454 to Jiang et al., and US Published Applications2007/0236861 to Burdon et al., 2007/00609969 to Burdon at al.,2011/0102967 to Munns et al., and 2011/0248184 to Shah. None of theprior art concepts, however, including the prominent concepts notedabove, teaches a structure that has a mutually conformal interface, alsocalled a tortuous, intimate knitline, that results in sustainablehermeticity for an AIMD. Further, none of the prior art, including theprominent concepts noted above, teach a structure, or the manufacture ofsuch a structure, having residual stress levels such that either matchedhermetic structures or structures that have protectively compressivestresses from the ceramic part to the filled via at the bondinginterface are created.

Briefly discussing each of the prominent concepts provided above, U.S.Pat. No. 5,782,891 to Hassler et al. is directed to an implantableceramic enclosure which has a hermetically sealed substrate throughwhich vias pass. While Hassler teaches a ceramic substrate feedthroughco-fired with metallic conductive interconnects, these interconnects areeither staggered or are straight with a broad conductor (see HasslerFIG. 8). It is the staggering of the vias alone or in conjunction with abroad conductor that imparts hermeticity of the vias in this structure,and not a mutually conformal interface or tortuous, intimate knitlinefor a single straight via. Additionally, Hassler teaches selection ofmaterials to avoid shrinkage mismatch and not structures whereinshrinkage of the ceramic is greater than shrinkage of the filled viamaterial. Further Hassler does not teach a terminal or feedthroughhaving residual stress levels such that matched hermetic structures orstructures that have protectively compressive stresses from the ceramicpart to the filled via material at the bonding interface are created.

U.S. Pat. No. 6,146,743 to Haq et al. teaches hermetically sealedmultilayer substrates with vias. One is directed to Haq FIG. 16, whichhas been reproduced herein as FIG. 11. FIG. 11 shows the cross sectionof via fill after sintering. Haq discloses that the in this structurethe “ceramic powder component also improves the degree of adhesionbetween the ceramic forming the substrate itself and external via 66,thereby ensuring the formation of an hermetic seal in ceramic substrate50. This hermetic seal inhibits or prevents internal metallizationlayers 64 from becoming oxidized when substrate 50 is air-fired duringone method of the present invention.” FIG. 11A is taken from section11A-11A from FIG. 11 and shows a blow-up of the internal micro-structureof the Haq post-sintered via 180. One is directed to Haq column 21,lines 32-43. Towards the end of that paragraph it states, “As theunfired green tape material emerges from the casting tape machine, it iscoated with a castable dielectric composition that upon firing at hightemperatures forms a glass.” It is the external via that impartshermeticity of the internal vias in this structure, and not a mutuallyconformal interface or tortuous, intimate knitline for a single straightvia. Regarding shrinkage, Haq teaches matching shrinkages betweenceramic and filled via material. Haq does not teach a structure whereinshrinkage of the ceramic is greater than shrinkage of the filled viamaterial. Further Haq does not teach a terminal or feedthrough havingresidual stress levels such that matched hermetic structures orstructures that have protectively compressive stresses from the ceramicpart to the filled via material at the bonding interface are created.

U.S. Pat. No. 6,414,835 to Wolf et al. discloses “hermetically sealingthe common substrate edge to the ferrule inner wall within the centrallydisposed ferrule opening and electrically coupling the plurality ofsubstrate ground paths to the ferrule”, and claims a “plurality ofsubstrate conductive paths extending through the co-fired metal-ceramicsubstrate between the internally and externally facing layer surfacesand electrically isolated from one another further comprise a pluralityof electrically conductive vias extending through via holes of theplurality of layer thicknesses and a plurality of electricallyconductive traces formed on certain of the internally or externallyfacing layer surfaces such that the conductive traces join theconductive vias to form each substrate conductive path.” FIG. 5 of Wolfet al. illustrates this as staggered vias. Further the vias in FIG. 5 ofWolf are subsequently covered with biocompatible end caps 70 andbiocompatible gold brazes 80 on the body fluid side. It is thestaggering of the vias in conjunction with the end caps that impartshermeticity of the vias in this structure, and not a mutually conformalinterface or tortuous, intimate knitline for a single straight via. Wolfteaches trimming laminated ceramic layers to account for shrinkage andalso compression of the co-fired substrate by the ferrule. Wolf,however, does not teach structures wherein shrinkage of the ceramic isgreater than shrinkage of the filled via material. Further Wolf does notteach a terminal or feedthrough having residual stress levels such thatmatched hermetic structures or structures that have protectivelycompressive stresses from the ceramic part to the filled via material atthe bonding interface are created.

U.S. Pat. No. 8,000,804 to Wessendorf et al. illustrates an electrodearray for a neurostimulator. The Wessendorf patent teaches “a pluralityof electrodes arranged in a two-dimensional array and extending throughthe ceramic base between the first and second major surfaces; a ceramiclid having a plurality of electrical connections extending therethrough,with the ceramic lid being attachable to the ceramic base to form ahermetically-sealed interior region; and an electronic circuit (e.g. ademultiplexer circuit) located within the hermetically-sealed interiorregion.” Hermeticity in this case is imparted by “a two-part ceramicpackage which can be hermetically sealed” and not by a mutuallyconformal interface or tortuous, intimate knitline for each singlestraight via. Wessendorf teaches matching CTEs for ceramic and via fillmaterials, however, Wessendorf does not teach structures whereinshrinkage of the ceramic is greater than shrinkage of the filled viamaterial. Further Wessendorf does not teach a terminal or feedthroughhaving residual stress levels such that matched hermetic structures orstructures that have protectively compressive stresses from the ceramicpart to the filled via material at the bonding interface are created.

U.S. Pat. No. 8,043,454 to Jiang et al. describes a method of making ahermetic via in a ceramic substrate that is composed of a noble metalpowder in a glass-free paste that contains alumina and a mixture ofniobium pentoxide. The addition of the niobium pentoxide to thepre-sintered paste prevents shrinkage of the paste during thermalprocessing and binds to both the ceramic and the noble metalparticulates in the via, thus maintaining a hermetic seal around thevia. Hence, hermeticity in this case is imparted by niobium pentoxideand not a mutually conformal interface or tortuous, intimate knitlinefor a single straight via. Jiang teaches avoiding CTE mismatches forfeedthroughs and compression seals formed by metal tubing on ceramicinsulators, however, Jiang does not teach structures wherein shrinkageof the ceramic is greater than shrinkage of the filled via material.Further Jiang does not teach a terminal or feedthrough having residualstress levels such that matched hermetic structures or structures thathave protectively compressive stresses from the ceramic part to thefilled via material at the bonding interface are created.

U.S. Patent Publications 2007/0236861 and 2007/0060969 both to Burdon etal. disclose hermetic interconnects for implantable medical devices. Oneembodiment includes a conductive material introduced to a via in asingle layer. Also disclosed are alumina ceramic with vias in which theconductive material may be platinum. Both publications discuss terminalassemblies comprising staggered vias only. Hermeticity in thesestructures is imparted by the staggered vias and not by a mutuallyconformal interface or tortuous, intimate knitline for a single straightvia. Neither application teaches structures wherein shrinkage of theceramic is greater than shrinkage of the filled via material. Furtherneither application discusses or teaches a terminal or feedthroughhaving residual stress levels such that matched hermetic structures orstructures that have protectively compressive stresses from the ceramicpart to the filled via material at the bonding interface are created.

U.S. Patent Publication 2011/0102967 to Munn et al. discloses amultilayered feedthrough for an implantable medical device that includesa substrate having a first edge, a second edge, and a substrate length.A plurality of traces is formed on the substrate and extends along thesubstrate length. The plurality of traces extends to the first andsecond edges of the substrate. An insulator layer is formed on thesubstrate and the plurality of traces. A ground plane layer is formed onthe insulator layer. Munn FIG. 7 shows the individual vias of thisstructured captive within these substrates which in turn impartshermeticity to this structure and not by a mutually conformal interfaceor tortuous, intimate knitline for a single straight via. Munn does notdiscuss or teach structures wherein shrinkage of the ceramic is greaterthan shrinkage of the filled via material. Further Munn does not discussor teach a terminal or feedthrough having residual stress levels suchthat matched hermetic structures or structures that have protectivelycompressive stresses from the ceramic part to the filled via material atthe bonding interface are created.

U.S. Patent Publication 2011/0248184 by Shah reveals a sensor substratewith via holes. At least one of the via holes is hermetically sealedwith an optically transmissive material and not by a mutually conformalinterface or tortuous, intimate knitline for a single straight via. Shahdoes not discuss or teach structures wherein shrinkage of the ceramic isgreater than shrinkage of the filled via material. Further Shah does notdiscuss or teach a terminal or feedthrough having residual stress levelssuch that matched hermetic structures or structures that haveprotectively compressive stresses from the ceramic part to the filledvia material at the bonding interface are created.

In summary, none of the prior art concepts teach a structure that has amutually conformal interface or tortuous, intimate knitline that resultsin sustainable hermeticity for an AIMD, has higher shrinkage of theceramic than of via fill material, or possesses residual stress levelssuch that matched hermetic structures or structures that haveprotectively compressive stresses from the ceramic part to the filledvia material at the bonding interface are created.

It is understood that “vias” are defined as holes, apertures, conduits,or voids created in either insulators or capacitors. A via can also befilled with a conductive material or bore-coated with a conductivematerial such that the inside surface is metalized and conductivelycoated. A via in a capacitor will generally be referred to as acapacitor via. A via in an insulator will generally be referred to as aninsulator via. Accordingly, the terms filled or bore-coated can also beapplied to either capacitor vias or insulator vias.

FIG. 9 illustrates a prior art cross-section of a different type ofhermetic terminal subassembly substrate 120 via fill. The insulator 120is a ceramic substrate formed by roll compaction. After compaction, theleadwire 180 is placed within the insulator via. In this case, theinsulator via is filled with a solid platinum leadwire 180. One isreferred to U.S. Pat. Nos. 7,480,988; 7,989,080; and 8,163,397. Thesethree patents share a common priority chain and are directed to a methodand apparatus for providing a hermetic electrical feedthrough. All threeof these patents were assigned to Second Sight Medical Products, Inc.and will hereinafter be referred to as the “Second Sight” patents. FIG.3 of the Second Sight patents is a flow process that starts withdrilling blind holes in a green ceramic sheet. Then lengths of platinumleadwire 180 are cut and inserted into the sheet holes in step 39. Theceramic wire assembly is then fired at 1600° C. in step 44. Second Sightdiscloses that “during the firing and subsequent cooling, the ceramicexpands shrinking the holes around the wires 38 to form a compressionseal. The shrinkage is believed to occur, at least in part, as aconsequence of polymer binder burnout. The fine aluminum oxidesuspension permits uniform and continuous sealing around the surface ofthe wire. Additionally, at the maximum firing temperature, e.g.,1600.degree. C., the solid platinum wires being squeezed by the ceramicexhibit sufficient plasticity to enable the platinum to flow and fillany crevices. This action produces a hermetic metal/ceramic interface.”Further, Second Sight discusses that “After lapping, the feedthroughassembly comprised of the finished ceramic sheet and feedthrough wires,is subjected to a hermeticity test, e.g., frequently a helium leak testas represented by block 56 in FIG. 3.” While Second Sight discussesforming a compression seal and platinum flow to fill any crevices,creation of mutually conformal interface or tortuous, intimate knitlinebetween the alumina and the platinum wire is not taught.

In addition, latent hermetic failures in device feedthrough terminalshave been known to occur due to susceptibility of the glass phasedinterface between these mating materials to erosion by body fluids. Thisoutcome is particularly prevalent for interfaces comprising silicateglasses that are often a result of the additives to ceramic slurriesforming the tapes and via fill materials that are used to buildmultilayer ceramic feedthrough structures. Dissolution of silicateglasses is composition dependent. In particular, erosion of silicateglasses in the body typically occurs when the silica content is lowerthan about 60%. Silica glasses, as suggested by the name, are based on atetrahedral network of atoms comprising silicon and oxygen covalentlybonded to each other. Heat treatment during the assembly process of thefeedthrough structure provides the means by which other elements, suchas alkali and/or alkaline ions, can be introduced into the silica atomicnetwork. When the glass composition formed at the interface is more than60% silica, the atomic network within the glass structure typicallybecomes resistant to reaction with body fluids due to the dense natureof the atomic network structure. However, when the glass compositionformed at the interface is less than about 60%, the glass structure ismore susceptible to atomic structural degradation.

Degradation is generally due to the disruption of the silica atomicnetwork within the glass structure by other elements, such as alkaliand/or alkaline ions, introduced during binder bake out and sintering.These other elements are typically introduced into the feedthroughstructure from additives used within the green alumina tape or the viafill materials, such as the platinum paste, or both. For example, if theadditives in either material make available alkali-metal atoms forexchange with silicon atoms within the silica atomic network, and if theresult is an interface having a silica weight percent below about 60%,then rapid ion exchange of the alkali-metal cations with hydrogen ionsfrom body fluid typically occurs. This results in the formation offunctional hydroxyl, or —OH, groups that are highly reactive in thebody, breaking down and weakening the atomic network structure of theglass phased interface thus increasing the likelihood of a breach in thehermeticity of the feedthrough terminal. Hence, hermetic structurescreated by mating alumina and platinum are not obvious and any inherencyin the bond developed between these two materials does not necessarilyresult in a biocompatible final structure that can sustain hermeticityover the service life of an AIMD.

Once again referring to U.S. Pat. No. 8,043,454 of Jiang et al., insharp contrast to the present invention, Jiang adds between 1-10 percentby weight of niobium pentoxide. Another way to look at this is in thepresent invention, organic binders and solvents are used as opposed toinorganic additives. Referring once again to FIG. 11A, additives to theplatinum via fill 180 such as disclosed by Haq may result in unfavorablefunctionality. For example, the elongate channel-like structures 184that are actually a result of additives like ceramic powder can lowerelectrical conductivity if the conductivities of these phases aresignificantly different from the primary densified material formed. Thisis discussed in some of the prior art cited. It is very important forhuman implant applications that the resistivity of the filled via holesbe as low as possible. The inventors have found that adding any ceramicpowder to the platinum paste substantially increases the electricalresistivity of the post sintered via hole. This is a major reason whythe inventors have been working over a number of years to develop a pureplatinum sintered via hole. This is particularly important for AIMDs,such as implantable cardioverter defibrillators. An implantablecardioverter defibrillator not only senses electrical activity, but itmust be able to deliver a very high voltage and high current shock inorder to defibrillate the patient. This means that the entire system,including the lead conductors, the hermetic terminal subassembly viaholes, and associated internal circuitry must have very low resistanceand low impedance so that a high current can be effectively delivered.Furthermore, and as noted above, the creation of a glassy-phasedstructure 184 bonded has the potential problem of latent hermetic leakswhen exposed to body fluid. The present invention resolves this issue.

In the present invention, a post sintered essentially high purityalumina substrate 188 with one or more via holes 186 that pass from anoutside surface of the alumina substrate 188 to an inside surface of thealumina substrate 188 is provided wherein, the via holes 186 comprise anon-toxic and biocompatible post sintered essentially pure platinumfill. There are several differences between the present invention andthe prior art in addition to those specifically discussed in the briefoverview of specific art cited. In the prior art, typically variousadditives are used to modify the alumina ceramic and/or the platinumpaste. In the prior art, at times, it is not even a pure platinum pastethat is used (see Wessendorf column 5, line 29), but rather onecontaining other refractory type materials, such as tungsten or thelike. These additives are used to match the CTE during fabrication. Inother words, these prior art systems go to a lot of effort to match theceramic and metal parts of the system so that cracking or loss ofhermeticity between the alumina substrate 188 and via 186 does not occurover time. Additionally, much of the prior art processes lay down a thinlayer of ceramic tape, then use thick-film screen printing or othermethods to deposit circuit traces and filler for the previouslyfabricated via holes 180. These fillers include tungsten inks and thelike. Then, these individual layers are dried, stacked up and pressed(laminated) into a bar. There are often registration errors andstair-stepping is visible in the cross-sections of such vias 180.

In the present invention, via holes are not formed in individual tapelayers before stack-up. Instead, the alumina ceramic slurry can bethick-cast into tape and then laid down in layers or it may be injected,molded, powder pressed or the like to form a single monolithicstructure. In this state, the alumina ceramic is still in the green andvery pliable due to the organic binders and solvents that have beentemporarily added to the system. It is at this point that via holes 186are drilled therethrough from the outer surface (body fluid side) to aninner surface (AIMD electronic side) of the alumina substrate 188.Because the holes are drilled after formation of the pre-sinteredceramic substrate 188, there is no requirement for registration with theconsequential “stair-stepping” (due to misregistration) that is visiblein cross sections of some prior art structures, for example thosedescribed in the Second Sight patents.

After via holes are formed, the pure platinum paste composition isinjected under pressure or via vacuum into the via holes 186. Thepressure or vacuum is carefully controlled in the present invention sothat the platinum paste is driven intimately along the surface of theinside of the via such that the paste conforms to and creates a mirrorimage of the inner surface of the via in the alumina ceramic and, in sodoing, interconnect with the already tortuous members prevalent inceramic/particulate formation. A mutually conforming interface 191 isthereby formed between the platinum fill and the inside diameter of thevia hole in the ceramic. Drilling is a preferred method of forming thevia hole, but these via holes may also be formed by punching, laserdrilling, water cutting or any other equivalent process.

As used herein, the term “essentially high purity alumina” means aluminaceramic with the chemical formula Al₂O₃. “Essentially pure” means thatthe post-sintered ceramic is at least 96% alumina. In a preferredembodiment, the post-sintered ceramic is at least 99% high purityalumina. Prior to sintering, the alumina may be a paste, a slurry orgreen state, and can contain organic solvents and binders. Once theseorganic solvents and binders are baked out, the alumina is sinteredbecoming essentially high purity alumina. Similarly, prior to sintering,the platinum paste also contains binders and solvents. The drilled viasof the ceramic insulator are filled with the platinum paste. It is afterthe binders and solvents are baked out at elevated temperature and thensintered that they are substantially removed and an essentially pureplatinum via hole is created.

One is referred to FIG. 12 which is a flow chart illustrating the mainsteps of the process of the present invention. First, an essentiallyhigh purity alumina substrate is formed. The essentially high purityalumina can be formed either through injection molding, green machining,powder pressing 166, by pressing powder into an injection die, or bytape casting and then stacking and laminating individual layers, under apressure ranging from about 1,000 psi to about 5,000 psi at atemperature ranging from about 60° C. to about 85° C. for about 5minutes to about 15 minutes into a bar 168. After formation of the barin step 168, the via holes are formed preferably by drilling through thestructure, however punching, pressing, laser or waterjet operations mayalso be used to form the holes 170. All of the via holes would be filledin step 172 with an essentially pure platinum paste containing organicsolvents and organic binders. It should be noted that organic solventsand binders also make up a percentage of the green essentially highpurity alumina substrate. A further clarification is required here. Asused herein, “essentially pure” means essentially pure post-sinteringonce the bulk of the binders and solvents have been baked out in step174 and/or sintered in step 176, both at elevated temperature. Once thebinders and solvents have been driven out of the system and sintering176 has occurred, the result is a solid monolithic high purity aluminasubstrate 188 with one or more pure platinum via holes 186 extendingfrom an alumina substrate 188 outer surface to an inner surface. Theoutside diameter or the perimeter of the alumina substrate can now beprepared for attaching a ferrule 122 as previously illustrated in FIGS.5, 7 and 8. In the present invention, the ferrule 122 is attached usingconventional prior art techniques. That is, the outside diameter orperimeter of the sintered alumina substrate 188 is metalized(sputtered). The metallization would typically be in two layers with afirst layer being an adhesion layer and the second layer being a wettinglayer, 178. Then the ferrule is attached to these metalized ceramiclayers through a gold brazing process 178 wherein, pure gold is reflowedsuch that it wets the titanium ferrule and also wets to the metalizedsurfaces that were previously sputtered onto the alumina ceramic. Again,this ferrule attachment method is very common in the prior art.

The present invention centers around three enabling areas: (1) viapacking with a high solids loading in the paste, (2) compression by theceramic of the metal paste during binder bake out and sintering, and (3)a controlled cool down rate in combination with interfacial bondingsufficient to tolerate coefficient of thermal expansion (CTE) mismatch.

Metal/ceramic compatibility is an important factor in manufacturinghermetic terminals. The difference in CTEs of the metal and ceramic isrecognized as a major parameter in predicting compatibility. The thermalexpansion of metal is generally considerably greater than those ofceramics. For example, at a bakeout temperature of 500° C., the CTE ofalumina is 7.8×10⁻⁶/K and of platinum is 9.6×10⁻⁶/K. Historically, CTEdifferences within 0.5 to 1.0×10⁻⁶/K between the mating metal andceramic materials are adequate to sustain hermetic bonding between thesematerials. However, it is believed differences beyond these limitsprovided at the bake out temperature for the alumina/platinum pair mayproduce sufficient tensile stresses at the interface during cool down tocause spontaneous bonding failure. Hence, given the significantdifference in CTEs, even at a relatively low temperature of 500° C.,achieving a hermetic seal between the platinum metal and alumina ceramicwould not be expected if the difference in CTE between the sinteredalumina and the platinum metal exceeds 0.5 to 1.0×10⁻⁶/K. Rather, thepresent invention achieves a hermetic feedthrough structure through thecontrolled fabrication process parameters of the platinum metal particlesolids loading within the paste, controlled packing of the platinumpaste within the via, and the controlled shrinkage of the aluminasubstrate and platinum via paste through a prescribed co-fire heatingprofile.

In addition, a highly irregular surface at the material interfacebetween the alumina substrate and the platinum metal particles withinthe via provides a mechanical contribution to adherence and robustnessof the hermetic seal. A surface roughness produced by drill bits,sandblasting, gritblasting or chemical etching of the metal substratecan increase the surface area and, in so doing, provide for a strongermechanical attachment along the mutually conformal interface. Applyingthis concept to the alumina/platinum interface therein provides foranother novel aspect of the present invention. Examples of sandblastingand gritblasting media include sand, sodium bicarbonate, walnut shells,alumina particles or other equivalent media.

In the present invention, to achieve sustainable hermeticity, thefollowing is required. Because the CTE of platinum is sufficientlyhigher than the CTE of alumina, it is not theoretically possible foralumina to provide compressive forces on a platinum body in a via.Hence, to overcome the CTE differences between these two materials, theplatinum body in the via must be formed using a paste, a slurry or thelike, having a minimum of 80% solids loading. In a preferred embodiment,the solids loading of the platinum particles within the paste is 90%. Ina more preferred embodiment, the solids loading of the platinumparticles within the paste is 95%. In addition, the via must be packedwith the platinum paste to occupy at least 90% of the available spacewithin each via opening. In a preferred embodiment, the platinum pasteis packed within the via opening to occupy 95% of the space. In a morepreferred embodiment, the platinum paste is packed to occupy 99% of thevia opening. The shrinkage of the alumina must be no greater than 20% ofthat of the platinum fill in the via. In a preferred embodiment,shrinkage is 14%. In a more preferred embodiment, shrinkage is 16%.

Furthermore, the assembly is exposed to a controlled co-firing heatingprofile in ambient air that comprises a binder bakeout portion, asintering portion and a cool down portion. In an embodiment, the binderbakeout portion is performed at a temperature of between 400° C. to 700°C. for a minimum of 4 hours. A preferred binder bakeout is at atemperature of between 550° C. to 650° C. A more preferred binderbakeout is at a temperature of between 500° C. to 600° C. The sinteringprofile portion is preferably performed at a temperature ranging from1,400° C. to 1,900° C. for up to 6 hours. A preferred sintering profilehas a temperature between 1,500° C. to 1,800° C. A more preferredsintering temperature is between 1,600° C. to 1,700° C. The cool downportion occurs either by turning off the heating chamber and allowingthe chamber to equalize to room temperature or, preferably by settingthe cool down portion at a rate of up to 5° C./min from the holdtemperature cooled down to about 1,000° C. At 1,000° C., the chamber isallowed to naturally equalize to room temperature. A more preferred cooldown is at a rate of 1° C./min from the hold temperature to about 1,000°C. and then allowing the heating chamber to naturally equalize to roomtemperature. In so doing, the desired outcome of achieving a robusthermetic seal is achieved between the mating materials of the aluminaand platinum. It is noted that these materials have a CTE mismatchbeyond the limits heretofor recognized as adequate for sustainedbonding.

During processing of the platinum fill densities and additionally duringthe densification phase, compression is imparted by the alumina aroundthe platinum within the via due to the shrinkage of the alumina beinggreater than that of the platinum. Furthermore, the platinum issufficiently malleable at this phase to favorably deform by thecompressive forces being applied by the alumina. The combination of theplatinum solids loading, the platinum packing in the via and theshrinkage of the alumina being greater than the platinum fill results inthe platinum taking the shape of the mating alumina surface. The amountof platinum solids loading, its packing percentage within the via andthe malleability of the platinum material all contribute to formation ofa hermetic seal between the platinum and alumina. In addition, thecompressive forces that result from the greater shrinkage of the aluminasubstrate than that of the platinum within the via limit expansion ofthe platinum and force the platinum to deform such that it forms ahermetic seal. Thus an interface between the alumina and platinummaterials that conforms to the respective interface surfaces and resultsin a nearly exact mirror image of the interfacing surfaces is formed,thereby creating a hermetic bond therebetween. This mutually conformalinterface is critical, particularly as researchers studying bondingbetween alumina and platinum believe that any strength in the bondingbetween the alumina and platinum is physical.

As noted earlier, strong bonding between the alumina and the platinum isthe most important factor in achieving sustainable hermeticity infeedthrough terminals for AIMDs. The inventors have learned that theco-fire parameters used to form the hermetic terminals of the presentinvention provide unanticipated, but novel benefit of leveraging thecatalytic nature of platinum, that is, platinum's affinity for certainelements, which enables either direct bonding or formation of aninterfacial layer between the two materials. Analysis of the interfacebetween the alumina and the platinum of this invention disclosed notonly the creation of an intimate knitline, but, in the case of theinterfacial layer, a hermetic structure that exhibits an amorphous layerat the knitline comprising the elements platinum, aluminum, carbon andoxygen that appears to impart resistance to erosion by body fluids. Boththese bonding mechanisms, direct bonding and an amorphous interfaciallayer, offer additional tolerance to the CTE mismatch between these twomaterials.

FIGS. 13 and 14 are simplified unipolar cross-sectional views (withoutferrules) showing the essentially high purity alumina ceramic 188 of thepresent invention with a pure platinum via hole 186. The ceramic in FIG.13 has been formed from a single monolithic body, either throughinjection molding or green machining or the like. In contrast, FIG. 14illustrates that the alumina ceramic 188 has been formed by stacking upindividual tape layers L1, L2, L3 . . . Ln. In both cases, the platinumpaste 186 is injected into the via hole in such a way that it compactsand fills every ridge and valley of the inside diameter of the via holeitself imparting symmetry, intimacy and preserving tortuousity. Thissymmetry, intimacy and tortuousity, in turn, impart tolerance toshearing and/or tensile stresses that might develop during cool downand/or during service. Tolerance to these stresses, in turn, impartssustainable hermeticity over the service life of an AIMD. Forsimplicity, in FIGS. 13 and 14, the two side walls of the via hole areshown as straight lines. In reality, these via holes have an irregularedge with high spots, low spots, little ridges and so on, imparted bythe bound particulate materials used for the mating materials.

Referring back to FIGS. 13 and 14, one can see that there is a bodyfluid side and a device side of the platinum filled via 186. It isextremely critical, in this application, that the resistance or theresistivity from the body fluid side to the device side of the via holebe very low. This is critically important when an AIMD deliverstherapeutic pulses such that they not be attenuated which could resultin pulse degradation and/or reduced AIMD battery life. It is verycritical that resistance or resistivity be quite low in an implantablecardioverter defibrillator application. This is because the entire leadsystem, including the platinum filled via hole, must handle the veryhigh current monophasic or biphasic defibrillation shock pulse. Theresistance from the body fluid side to the device side of the platinumfilled via would be no greater than about 0.5 ohms. In anotherembodiment, the resistance from the body fluid side to the device sideof the platinum filled via would be no greater than about 0.3 ohms. Inanother embodiment, the resistance would be no greater than about 100milliohms. In another embodiment, the resistance would be no greaterthan about 10 milliohms. In another embodiment, the resistance would beno greater than about 2 milliohms.

FIG. 15 illustrates a co-fired high purity alumina hermetic terminalsubassembly with pure platinum filled vias 186 of the present invention.The pure platinum fill 186 forms a tortuous, intimate and mutuallyconformal interface 191 between the alumina dielectric insulatorsubstrate 188 and the platinum fill 186.

FIG. 16 is taken from section 16-16 from FIG. 15 and shows thepost-sintered condition wherein the platinum via 186 and the aluminaceramic 188 form a tortuous, intimate, mutually conformal interface 191.The peaks and valleys of this tortuous surface are very important in thepresent invention as it increases the surface area of the matingsurfaces which offers interfacial intimacy that imparts tolerance formismatch in the CTE between the high purity alumina substrate 188 andthe sintered pure platinum via 186. During thermal excursion, stressescan develop at the interface between the alumina ceramic 188 and thepure platinum via 186 as shown in FIG. 16. This is where the tortuoussurface becomes very important. The ridges and valleys that existbetween the two surfaces of the interface 191 form an intimate structurecapable of withstanding compressive, tensile and sheer stresses. This isa result of a greatly increased contact surface area between thesintered alumina substrate material and the sintered pure platinum fill186. This greatly increased contact surface area improves the overallstrength and helps sustain hermeticity of the pure platinum-filled viahole. Helium leak rates of no greater than 1×10⁻⁷ std cc He/sec arereadily achieved using this novel process. In preferred embodiments, thehelium leak rate would be no greater than 1×10⁻⁸, 1×10⁻⁹, 1×10⁻¹⁰,1×10⁻¹¹ or even 1×10⁻¹² std cc He/sec.

Another important feature of the present invention is closed cellporosity 190 as shown in FIG. 15 in the pure platinum 186. This closedcell porosity 190, 190′, 190″ is best illustrated in FIG. 16, which is asectional view taken from section 16-16 from FIG. 15. Referring backagain to FIG. 16, one can see there are a number of closed pores 190,190′, 190″ and the like. First of all, in the present invention, thereare no ceramic powders, glasses or other additives (other than temporarybinders and solvents) to the platinum fill paste 186. Further, theplatinum fill paste comprises at least 80% solids. Accordingly, when thepresent invention is sintered, a dense filled via with carefullycontrolled, well distributed, closed-cell pores 190 forms. The presenceof these pores are not contiguous, and hence do not compromise thehermeticity of the overall via structure 186. Also, given that a densefilled via forms, these pores are relatively few in number so they haveminimal, if any, effect on the overall resistivity of the via hole fromone end to the other.

FIG. 17 is a novel hermetic seal of the present invention. It has somefeatures in common with prior art hermetic seals, particularly thoseillustrated in FIGS. 3, 5 and 8. The outside diameter of the aluminahermetic insulator 188 has metalized surfaces 150 and 152, which arewetting and adhesion surfaces, respectively, so that gold braze 140 canbe melted and hermetically bonded to the alumina hermetic insulator 188and the ferrule 122 of the hermetic terminal assembly 189. As in theprevious drawings, the ferrule 122 may be installed into the AIMDhousing 102 by laser welding 128, or the like. As previously mentioned,it is a major goal of the present invention to eliminate the highlyexpensive biocompatible and noble leadwires 118, as previouslyillustrated in FIGS. 3, 5 and 8. Referring once again to FIG. 17, it isapparent that instead of a feedthrough leadwire, the present inventioncomprises a pure platinum filled via hole 186. It is a novel feature ofthe present invention that this via hole material 186 be of essentiallypure platinum that is co-fired with the essentially high purity aluminaceramic substrate 188.

FIG. 17A is similar to FIG. 17 except that the ceramic body 188 has beenlaid down in individual tape layers. After sintering, these individuallayers form a monolithic structure and are very difficult, if notimpossible, to discern.

FIG. 17B is very similar to FIGS. 17 and 17A except that the novelplatinum filled via hole 186 has counter-bores 195 shown on both ends.It will be obvious to those skilled in the art that these counter-bores195 could be counter-sinks, counter-bores or any shape and they could beat both the top and the bottom of the substrate surfaces as shown. Theycould also be just on one side of the substrate (not shown). Thispermits use of a very thin diameter via hole which saves on the amountand expense of pure platinum while at the same time provides a largesurface area for a ball grid array attachment, for example, of afeedthrough capacitor as will be described in subsequent drawings.

FIG. 18 is very similar to FIGS. 17 and 17B except that a novel wirebond cap 192 has been placed on top of the via hole 186. In a preferredembodiment, this wire bond cap 192 could be of similar compatible metal,like pure platinum, such that it could be co-fired, to electrically andmechanically connect to the via hole fill material 186. This wire bondpad 192 can be placed on the top side as shown, or the bottom side, notshown, or both sides depending on the application and how wires would berouted to an implanted lead, an AIMD connector-header block, or thelike. Referring once again to FIG. 18, the novel cap 192 can be set intoa counter-bore hole as shown or it can be set flush or proud on the topsurface of the alumina 188, or any variation thereof. Referring onceagain to FIG. 18, an implantable lead conductor could be connected to awire bond pad 192 located on the body fluid side. In general, theimplantable lead conductor or header block leadwire 118 would have adistal electrode in contact with biological cells.

It has been demonstrated that in a normal patient environment, a patientcan be exposed to EMI. This EMI can take many forms, such as that fromcellular telephones, airport radars, microwave ovens, and the like. Anew international standard ISO 14117 has evolved, which includes testsstandards to which cardiac pacemakers and implantable defibrillatorsmust be exposed in order to be qualified by the FDA. There are similarspecifications for cochlear implants and neurostimulators. Accordingly,it is important to provide EMI filtering at the point of lead conductoringress into the interior of the AIMD. It is best to decouple highfrequency interference before it gets inside of the AIMD housing 102.Once inside an AIMD housing 102, as illustrated in FIG. 3, the EMI canundesirably cross-couple or re-radiate to sensitive circuits where itcan disrupt the proper functioning of the AIMD. In extreme cases,pacemaker inhibition has been documented which is immediatelylife-threatening for a pacemaker dependent patient. Accordingly, thereis a need in the present invention, to provide for EMI filtering at thepoint of implanted lead ingress into the implanted medical devicehousing 102.

FIG. 19A is a top view of the novel co-fired high purity alumina (Al₂O₃)hermetic terminal subassembly 189 with one or more pure platinum filledvias 186 of the present invention. This configuration illustrates thatthe present invention is capable of very large scale integration. Thatis, a hundred or even a thousand novel platinum filled vias 186 can beplaced in a high purity alumina substrate 188. In addition, these vias186 on the body fluid side may have a metal protrusion 193 which isco-fired into the platinum via 186. For example, the metal protrusion193 may be used to form a nerve stimulation electrode. Thisconfiguration would be ideal, for example, in a retinol stimulationapplication.

FIG. 19B is a sectional view taken from section 19B-19B of FIG. 19Aillustrating a high purity alumina 188 which is co-fired with the pureplatinum via fill 186. A neuro-electrode 193 is shown co-fired into theplatinum via 186. In a preferred embodiment, the neuro-electrode 193would be of platinum so it has a CTE identical to the platinum viamaterial. The neuro-electrode 193 can also comprise titanium, iridium,niobium, rhodium, and/or palladium.

FIG. 19C is a top view of a prior art quad polar hermetic feedthroughusing traditional leadwires 118 and gold braze techniques. This iswithin a diameter 121, which is typically between 0.100 and 0.140inches.

FIG. 19D is a top view very similar to FIG. 19C and is within the sameexact diameter 121 as previously described in FIG. 19C. FIG. 19D is adramatic illustration of the very large scale integration that can beaccomplished by the solid pure platinum via hole filling of the presentinvention. In this case, there are 25 via holes in the same spacepreviously occupied by the four vias illustrated in FIG. 19C.

FIG. 20 illustrates the present invention wherein, two castellationcavities 198 a and 198 b have been formed for convenient insertion ofMLCCs 194 a and 194 b. Internal circuit trace connections 196 a areprovided at 194 a which connect to the ground metallization adjacent theferrule 122. On the opposite side of the MLCC 194 a, there is aninternal ground circuit trace 196 b. Active circuit traces 196 b and 196c are connected to the via hole platinum fill 186. In this way, the twocapacitors 194 a and 194 b are electrically connected to the center viahole 186 and at their opposite ends they are also electrically connectedto ground through vias with metallization 150 and 152 to gold braze 140and, in turn, to the ferrule 122. Importantly, the ferrule 122 isconnected to the overall equipotential electromagnetic shield surface102 of the AIMD. This equipotential surface 102 is herein defined as aground. It will be obvious to those skilled in the art that one MLCC 194a may be used or a multiplicity of capacitors and individualcastellation holes could be used. In some applications, it would beuseful to use staggered values of MLCCs so that they are self-resonantat different frequencies. This allows them to filter over a much broaderrange of EMI frequencies. One is directed to U.S. Pat. Nos. 5,650,759and 5,896,627 which show MLCCs adjacent to a hermetic terminalsubassembly for human implant. The contents of these two patents areincorporated herein by reference. One is also directed to U.S. Pat. Nos.5,959,829 and 5,973,906 which show the advantage of staggering chipcapacitors and using specially formed chip capacitors. The contents ofthese two patents are also incorporated herein by reference.

Referring to FIGS. 20 and 21, it will be obvious to those skilled in theart that the MLCCs have terminations on each end, which connect tointernal electrode plates of opposite polarity. One set of groundelectrode plates will be electrically connected to circuit trace 196 a(electrical connection material not shown). The other end of the MLCC194 a will be connected to circuit trace 196 b. A similar constructionapplies to the second MLCC 194 b. Its ground electrodes are connected toground terminal 196 d and its active electrodes are connected to circuittrace 196 c. One can see that very short length circuit paths 196 areobtained wherein the MLCCs 194 act as variable frequency diverters. Thatis, at high frequencies, such as undesirable EMI frequencies, thecapacitors will present a low impedance and thereby divert unwanted oreven dangerous EMI coupled to the implanted lead(s). This EMI RF energywill be diverted through capacitors 194 a and 194 b to the ferrule 122and then harmlessly to the overall electromagnetic shield 102. As a sidenote, it would not work very well to place these two MLCCs at somedistance down on a circuit board inside of the AIMD housing 102. Theproblem with this is that EMI is drawn inside the AIMD housing where itcan cross-couple and re-radiate and cause numerous problems.

FIG. 22 is a cross-sectional view very similar to the quad polarhermetic terminal subassembly 116 and feedthrough capacitor 124previously illustrated in FIGS. 7 and 8. One is directed to U.S. Pat.No. 8,179,658, which is incorporated herein by this reference, whichshows a capacitor via within internal metallization electricallyconnected to a solid feedthrough leadwire. In the present invention,feedthrough capacitor 124 has been mounted directly to the surface ofthe co-fired high purity alumina (Al₂O₃) hermetic terminal subassembly189 with one or more pure platinum filled vias 186. The feedthroughcapacitor 124 is first placed on the bottom surface of the co-fired highpurity alumina (Al₂O₃) hermetic terminal subassembly 189 with one ormore pure platinum filled vias 186. In a preferred embodiment, anadhesively backed insulator washer 206 is used to affix the feedthroughcapacitor 124 onto the surface of the alumina substrate 188. The washer206 has four stamped holes which align with the platinum filled vias 186a through 186 d and corresponding feedthrough holes of the feedthroughcapacitor 124. There are two different methods of electrical attachmentto the feedthrough capacitor illustrated. In the left hand hole, we havea solid fill of a solder, braze or thermal-setting conductive material204. A simplified electrical attachment is shown on the right sidewherein, a solder bump or ball grid array (BGA) 202 is first dispensedand then the capacitor is aligned and placed over it. Then, temperatureis applied to reflow the solder into place as shown. The solder makeselectrical contact with the platinum filled via hole 186 and also withthe capacitor terminations 130. The way this core subassembly 189 makesconnection with implanted lead conductor or the leadwires 118 in aheader block connector assembly or internal circuit connections will beshown in subsequent drawings. In accordance with good EMC principles,the feedthrough capacitor 124 is disposed immediately at the point ofEMI ingress into the inside of the device housing 102. In this way, highfrequency EMI can be decoupled and diverted to the device housing 102without adversely effecting AIMD sensitive electronic circuits.Feedthrough capacitor 124 active electrode plate sets 134 a and 134 bare both connected to the capacitor inside diameter metallization 130.The capacitor ground electrode plate sets 136 make contact with thecapacitor outside diameter or perimeter metallization 132. An electricalconnection 148 is made from the capacitor outside diameter groundmetallization 132 and the gold braze 140 of ferrule 122. This makes alow impedance oxide free electrical connection which is superior forhigh frequency performance.

In comparison to the prior art leadwires 118 previously illustrated inFIGS. 7 and 8, the structure illustrated in FIG. 22 is ideal for roboticassembly. The problem has been one of the “forest of the trees.” Whenone has a hermetic seal with say, eight to a dozen long platinumleadwires running through it, it becomes impossible with a productionrobot, to insert a feedthrough capacitor down over all of those wires atonce. This takes a human hand a considerable amount of time to threadeach one of those leadwires through and finally then snug the capacitorup against the hermetic terminal subassembly 189. It will be apparent toone skilled in the art that the co-fired high purity alumina (Al₂O₃)hermetic terminal subassembly 189 with one or more pure platinum filledvias 186 can be inverted and put into a robotic fixture holder. Then,BGA (ball grid array) bumps 202 can be formed and even the insulativeepoxy surface can be robotically formed or dispensed. The capacitor maybe picked up by a pick and place robot with a vacuum head and perfectlyaligned in place and then the entire assembly is heated to the pointwhere the solder connections are made. This requires almost no humanlabor to accomplish compared to the highly intensive human labor ofprior art assemblies. For example, referring back to FIG. 8 in the priorart, it is labor intensive to dispense sufficient quantities ofelectrical connection material 146 and 146′. First the capacitor has tobe seated in place against the hermetic terminal subassembly. This isdone against a sealing washer 206. It is very important that this bedone under temperature and pressure such as there are no gaps or voids.Then, one can invert the assembly and using micro syringes, inject thethermal-setting conductive material 146 and 146′ as best they canbetween the lead and the hole in the feedthrough capacitor. In order toget this material to drop into place, one must put the entire assemblyinto a centrifuge for a few minutes. Centrifuging drives thesilver-filled thermally conductive adhesive down into place (partiallyfills the hole around the leadwire118). This material is then pre-curedand then an abrasive microblast procedure is used to remove excessmaterial that has gotten on top. This process is usually repeated fromthree to five times iteratively until the fill is void free and meetsproduct requirements. Each time one fills one must do a pre-cure of thethermal-setting conductive adhesive and then an abrasive microblastfollowed by a multiple cleaning steps to remove any residual grit blastmedia, all of which involves a tremendous amount of labor and productionyield issues. In contrast, the present invention of FIG. 22 isaccomplished in seconds with no need for centrifuging or excessivecleaning steps (or even any cleaning steps).

FIG. 22A is similar to FIG. 22 except that the ferrule 122 has beencompletely eliminated. The ferrule 122 tends to be very expensivebecause it is machined from pure titanium. Accordingly, elimination ofthe ferrule 122 substantially reduces expense. In FIG. 22A, there is adirect gold braze 140 between the AIMD housing 102 and the metallizationlayers 150 and 152 that are sputtered or plated on the co-fired highpurity alumina (Al₂O₃) hermetic terminal subassembly 189 with one ormore pure platinum filled vias 186. In this case, the AIMD housing 102has been stamped to form an L-bend 236. This L-bend 236 providesstrength and stiffness in the area of the penetration through thehousing 102 for mounting of the co-fired high purity alumina (Al₂O₃)hermetic terminal subassembly with one or more pure platinum filled vias186. It will be obvious to those skilled in the art that shapes otherthan the L-bend 236 could also be stamped to add strength.

FIG. 23 is a very similar structure to FIG. 22 in that it is a quadpolar feedthrough capacitor similar in function to what was previouslydescribed in FIGS. 7 and 8. In this case, the outside diameter orperimeter metallization 132 of the feedthrough capacitor has beencompletely eliminated. This also eliminates the need to form anelectrical connection 148 around the perimeter or diameter of thefeedthrough capacitor to the ferrule 122 and in turn, to case ground102. The reason for this is that ground electrode plates 200 have beenformed in the co-fired high purity alumina (Al₂O₃) hermetic terminalsubassembly 189 with one or more pure platinum filled vias 186 b, c ofthe present invention. One can see that the center via hole 208, whichis filled with pure platinum, is also electrically connected to aplurality of ground electrodes 200. These electrodes become grounded bymeans of being electrically connected to the adhesion and wetting layers150 and 152. It is to these layers that the gold braze 140 makes anelectrical and a hermetic connection between the ferrule 122 and thewetting layer 152. It is through this electrical connection that theground electrode plates 200 inside of the co-fired high purity alumina(Al₂O₃) hermetic terminal subassembly 189 with one or more pure platinumfilled vias 186 are formed. An internally grounded feedthrough capacitor124′ is co-bonded to the co-fired high purity alumina (Al₂O₃) hermeticterminal subassembly 189 with one or more pure platinum filled viasstructure 186. Internally grounded hermetic insulators, such asinsulator co-fired high purity alumina (Al₂O₃) hermetic terminalsubassembly 189 with one or more pure platinum filled vias 186 shown inFIG. 23, are further described in U.S. Pat. No. 7,035,076, the contentsof which are incorporated herein by reference. Internally groundedfeedthrough capacitors 124′ are described in U.S. Pat. Nos. 5,905,627,6,529,103, 6, 765,779 and 6,765,780, the contents all of which areincorporated herein by reference. The solid filled vias 186 of theco-fired high purity alumina (Al₂O₃) hermetic terminal subassembly 189enable the BGA 202 dispensing and rapid or robotic assembly of theinternally grounded feedthrough capacitor 124′ to the overall hermeticterminal subassembly 189.

FIG. 23A is similar to FIG. 23 except that the ferrule 122 has beeneliminated. This is similar to the elimination of the ferrule 122previously described in FIG. 22A except that in this case, the sides ofthe AIMD housing 102 do not have the L-shape previously described inFIG. 22A. Again, it will be obvious to those skilled in the art thatwhen the ferrule 122 is eliminated, a direct braze 140 to the AIMDhousing 102 can be accomplished by pre-forming the housing into a numberof different shapes or even planar as illustrated in FIG. 23A.

FIG. 24 illustrates the internal ground plate of the co-fired highpurity alumina (Al₂O₃) hermetic terminal subassembly 189 with one ormore pure platinum filled vias 186 taken from section 24-24 of FIG. 23.Again, this is a quad polar structure in that there are four activeleadwires 186 that are in contact with distal electrodes and biologicalcells. These four leadwires include 186 a, 186 b, 186 c and 186 d. Thecentral ground 208 does not have to come all the way to the body fluidsurface. It could be in a blind hole (not shown). Referring to FIG. 24,the ground plate material 200 is preferably made of pure platinum orequivalent circuit trace material. The ground plate material may alsocomprise tungsten, iridium, rhodium and/or palladium.

FIG. 25 is taken from section 25-25 of FIG. 23. Obviously, the isometricview of the device no longer conforms with FIG. 7 or 8 as it is nolonger quad polar. Referring back to FIG. 25, ten active poles or leadconductor circuits 186 a through 186 j are illustrated. In this case,there are four grounded vias 208 a through 208 d. These grounded viasare symmetrically located and placed adjacent the active traces 186 athrough 186 j. For example, referring to ground via 208 a, it is exactlycentered between active vias 186 a, 186 b, 186 f and 186 g. This is veryimportant so that a low inductance and low impedance exists across theentire ground plane 200. As an extreme example, let's imagine for aminute that there was only one ground via in FIG. 25 and that was groundvia 208 a. In other words, imagine removing the ground vias 208 b, 208 cand 208 d. This means that good EMI filtering would occur for vias 186a, 186 b, 186 f and 186 g as they are not very distant from the groundvia 208 a. However, a far different situation would occur for vias 186 eand 186 j. These would now be a long distance from the nearest groundvia 208 a and substantial inductance and resistance would result acrossthe ground plane 200. Therefore, there would not be nearly as effectiveEMI attenuation on these distant active electrode vias 186 e and 186 j.The use of solid platinum filled vias is conducive for very large scaleintegration. Literally, hundreds, if not thousands of through vias canbe placed in a small footprint, which makes this an excellentapplication for neurostimulation, retinal stimulation, and the like.

FIG. 26 is similar to FIG. 25, but in this case, it shows a number ofadvantages of the present invention that are not immediately obvious.First of all, there are a multiplicity of ground vias 208 which assurethat each one of the active vias 186 is a short distance in the groundplane 200 from a grounded via 208. Also shown is that if one has aparticularly sensitive circuit, such as a cardiac pacemaker sensecircuit, one could place extra grounded vias 208 in close proximity tothe active vias to further improve EMI filter attenuation. For example,vias 186 might connect to pacemaker sense circuits and these are placedin very close proximity to ground vias 208 on both sides. Vias also donot have to be the same diameter. Vias 186′ are active circuit traces,but are shown larger than vias 186. This might be necessary when largetherapeutic pacing pulses are required, or in particular, for deliveryof high currents during a high voltage shock from an implantablecardioverter defibrillator. FIG. 26 is only an example of one type ofvery large scale integration. With the solid platinum-filled viatechnology of the present invention, it is possible to have hundreds ifnot thousands of vias in a very small footprint. This makes the presentinvention ideal for neurostimulators, retinal stimulators and the like.

FIG. 27 is similar to FIG. 2 in that it shows a prior art AIMD with aheader block connector assembly 104. In this case, the device 100C is acardiac pacemaker and the header block connector assembly ports 106,106′ are IS-1 or DF-1 ISO Standard connector cavities. These aredesigned to receive the proximal plug of implanted leads 108, aspreviously illustrated in FIG. 3. Leadwires 118 a, 118 b, 118 c and 118d within the header block connector assembly that are routed to thehermetic terminal subassembly 116, which has a ferrule 122 that has beenlaser welded into the housing 102 of the AIMD. In general, the headerblock connector assembly material 104 is not metallic. Most prior artheader block connector assemblies are some sort of polymer material,such as Techothane, or the like. A prior art feedthrough capacitor 124,which was previously illustrated in FIG. 3, is also shown. The routingof the leadwires 118 a, 118 b, 118 c and 118 d in the header blockconnector assembly is a difficult operation. In most cases, jigs andfixtures are used to hold all the components of the connector assemblies106 and 106′ in place while laser welding and attaching at theappropriate electrical contact points of the leadwires 118 takes place.In prior art EMI hermetic terminal subassemblies 116, these leadwiresare typically quite long and of a biocompatible material, such asplatinum iridium. In this configuration, it is required to preassembleall of the components, including the leadwires and then cast theTechothane in place. This is a difficult process because the Techothanemust be cosmetically pleasing and completely free from any voids or airbubbles. Accordingly, an improved method of header block connectorassembly construction and attachment is needed.

FIG. 28 illustrates a novel header block connector assembly 225 of thepresent invention, which incorporates a side window 210. Thisconstruction allows the connector components 106 and 106′ and theirassociated leadwires 118 to all be preassembled and then pre-molded in aseparate operation. This allows the header block connector assembly 225to be completely preassembled and pre-inspected and then later attachedto the pacemaker housing 102. The leadwires 118 are routed and designedto hang down into the window space 210 where they can be attached laterby laser welding, or the like, to contact pads 212 which are on theco-fired high purity alumina (Al₂O₃) hermetic terminal subassembly withone or more pure platinum filled vias 186 of the present invention. Onewill also see that there is a novel ball grid array attached feedthroughcapacitor 124. The ball grid array attachments are shown as 202.

Referring once again to FIG. 28, illustrated are internal leadwires 118′which are routed from the novel feedthrough capacitor 124 to circuitboard 126. The feedthrough capacitor 124 is novel due to a unique methodof inexpensive leadwire attach during the ball grid array 202attachment. Referring once again to FIG. 28, it will be appreciated thatone is looking at the side view of two IS-1/DF-1 style connector ports106, 106′. There are actually four connectors in the device 100C, but inthe side view, one can only see the two 106 and 106′. This makes for atotal of eight leadwires 118. Again, for simplicity, only fourleadwires118 are shown in the FIG. 28 side view, but one skilled in theart recognizes any number of leadwires may be used with the presentinvention.

FIG. 29 is an exploded view of the novel co-fired high purity alumina(Al₂O₃) hermetic terminal subassembly 189 with one or more pure platinumfilled vias 186. First of all, FIG. 29 shows a very novel way to attacha wire bond pad 212 to the novel pure platinum filled via holes 186 ofthe present invention. Wire bond pad 212 e is shown exploded away fromthe co-fired high purity alumina (Al₂O₃) hermetic terminal subassembly189 with one or more pure platinum filled vias 186. It is L-shaped tofacilitate wire bonding in the novel window 210 of the header blockconnector assembly 225 as previously illustrated in FIG. 28. Attachmentof these L-shaped wire bond pads 212 is done by an electrical attachmentmaterial 226. Since this is on the body fluid side of the invention, itis important that this electrical attachment material be non-toxic andbiocompatible. This can be a laser weld, a gold braze, a thermal-settingconductive adhesive, or the like. Long term biocompatiblethermal-setting conductive adhesive would usually be loaded with a pureplatinum, gold, or silver flake material.

Referring once again to FIG. 29, one can see that the side mounted wirebond pad 212 is suitable for attachment of a variety of types, shapesand sizes of leadwires which would be extending down into the headerblock connector assembly window 210. For example, leadwire 216, 118could be oval, leadwire 218,118 could be a flat ribbon wire, leadwire220, 118 could be a braided or stranded wire, leadwire 222, 118 could bea coiled wire and of course, leadwire 224, 118 could be a simple roundwire. Internal AIMD leadwires 118′ are shown as they exit thefeedthrough capacitor 124 and are directed to AIMD internal circuits,for example, to AIMD circuit board 126 previously illustrated in FIG.28. The various leadwires 216 through 224 are attached to the wire bondpads 212 using an electrical attachment material 214. In a preferredembodiment, the electrical attachment would be done by laser welding.Referring once again to FIG. 28, the window 210 is left open for easyaccess by laser welders or resistance wire bonders, or the like. Theheader block connector assembly 225 window 210 is left open until theleadwires are attached to the associated wire bond pads 212. In apreferred embodiment, a silicone or similar adhesive would beback-filled into the hole to prevent the ingress of body fluids and thelike.

FIG. 29a illustrates a paddle lead 225 electrically attached 214 toheader block connector assembly 212 as previously illustrated in FIG.29.

FIG. 29b illustrates the rectangular or ribbon lead 218 electricalconnection 214 to header block connector assembly 212 as previouslyillustrated as lead 218 in FIG. 29.

FIG. 30 is taken generally from section 30-30 from FIG. 29 and shows theco-fired high purity alumina (Al₂O₃) hermetic terminal subassembly 189with one or more pure platinum filled vias 186 of the present inventionin sectional view along with the BGA 202 mounted feedthrough capacitor124. The L-shape bonding pads 212 and their electrical attachment to theplatinum filled via 186 has already been described as electricalattachment 226. FIG. 30 illustrates novel leadwires 118′ which areinternal to the AIMD. On the right hand side, the leadwire is shown notyet inserted into the hole of the feedthrough capacitor 124. A majoradvantage of this leadwire 118′ is that it does not need to be non-toxicor biocompatible. The reason for this is that internal leadwires andcircuits are inside the hermetically sealed housing 102 of the AIMD 100.In a preferred embodiment, leadwire 118′ would be either bare orinsulated 230 copper leadwire. As shown in FIG. 30, a portion of theinsulation 230 has been removed. Again, in a preferred embodiment, theexposed tip 228 of the leadwire would either be tinned or solder dipped.This is better understood by referring to FIG. 31, which is a blow upview taken from section 31-31 of FIG. 30. Shown is leadwire 118′ andinsulation 230. It also shows the bare and solder-coated surface 228.When the entire assembly is heated such that the BGA solder 202 isreflowed, the BGA solder 202′ flows not only to the platinum filled via186, but also reflows with the solder coating on wire 228 therebycompleting an electrical circuit. This has a major advantage over all ofthe prior art, in that, the expensive platinum iridium or equivalentleadwire has been completely eliminated and replaced by a veryinexpensive leadwire 118′.

FIG. 32 is similar to FIG. 30 except that, in this case, the L-shapewire bond pads 212 a′ and 212 h′ no longer have a hole in the top. Inother words, there is no place for electrical connection material 226.Instead, there is a gold braze or equivalent 232 a which is capturedunderneath the bond pad 212 and is disposed adjacent the platinum filledvia 186 of the co-fired high purity alumina (Al₂O₃) hermetic terminalsubassembly.

FIG. 33 is similar to FIGS. 30 and 32 except that a radius 234 has beenadded to the corner of the co-fired high purity alumina (Al₂O₃) hermeticterminal subassembly with one or more pure platinum filled vias 186.This radius corner is important to eliminate stress risers which couldlead to fracturing in the corner during laser weld attachment 214 ofleadwires 224, 118.

FIG. 34 is similar to FIG. 32 and simply illustrates that in any of theembodiments described herein, leadwires 118′ are part of a solder reflowprocess wherein, an attachment is made from the platinum filled vias186, to the active electrode plates of the capacitor 124 and in turn, toleadwire 118′. In other words, the BGA solder joint 202 accomplishesthree very important functions. During high temperature reflow of theBGA solder 202, a connection is made between the platinum filled via186, the inside diameter terminations of the capacitor 130, and to theconductive portion of the leadwire 228.

FIG. 35 is similar to FIG. 30. There is a difference in the L-shapedwire bond cap 212. In this case, there is a hole in the wire bond capthrough which a pin 242 is either laser welded, brazed or the like 238to the L-shaped wire bond cap 212. This pin ideally would be of platinumor similar compatible metal. This assembly is co-fired along with thepure platinum via fill 186 so that a solid mechanical and electricalconnection is made between the pin 240 and the platinum via material186. There is also a difference in the way that the interior leadwires118′ are attached to the feedthrough capacitor 124. This is a specialfeedthrough capacitor that is rectangular in shape. The rectangularshape is better understood by looking at the cross-sectional views shownin FIGS. 36 and 37. FIG. 36 is taken generally along section 36-36 ofFIG. 35. FIG. 37 is generally taken from section 37-37 of FIG. 35. Theview in FIG. 35, therefore, is the end view of a rectangular structure.The active electrodes 134 are brought out to the sides of the capacitor,which is better illustrated in FIG. 36. This allows wire bond pads 246to be attached to the capacitor. Attachment is done by thermal-settingconductive adhesives, gold braze, high temperature solders, or the like248. The capacitor ground plate set 136 is terminated at its ends. Thisis important so that the ground plates 136 do not short to the activeelectrode plates 134. This makes subsequent attachment of interiorleadwires 118′ very easy. Internal leadwires 118′ can be attached to thewire bond pads 246 by thermal sonic bonding, resistance bonding,resistance welding, soldering, thermal-setting conductive adhesives,brazes, or the like, 244.

FIG. 38 illustrates a round quad polar co-fired high purity alumina(Al₂O₃) hermetic terminal subassembly with one or more pure platinumfilled vias 186 of the present invention. Shown are novel L-shaped wirebond pads 250 a through 250 d, which can be co-fired with the pureplatinum via hole fill 186. Since these wire bond pads 250 are on thebody fluid side, it is important that they be non-toxic andbiocompatible. Ideally, they would be of platinum or similar metal thatwas readily co-fired and matched to the CTE of the solid platinum viafill 186.

FIGS. 39 through 42 illustrate alternative shapes for the wire bond pads250A through 250D previously illustrated in FIG. 38. Each wire bond padhas one or more respective downwardly extending extrusions 250A′ to250D′ in order to penetrate the via hole platinum paste 186 so that whenco-firing, a solid mechanical and electrical connection is made.

FIG. 43 illustrates the co-fired high purity alumina (Al₂O₃) hermeticterminal subassembly 189 with one or more pure platinum filled vias 186of the present invention wherein, the alumina ceramic 188 protrudestowards the body fluid side well above the ferrule 122. There arecastellations 254 formed into the side of the alumina ceramic 188 toconveniently hold and register wire bond pads 252. The wire bond pad 252can have a pin or extrusion 250A′ to 250D′ as shown in FIGS. 39 to 42coming out the bottom wherein, the extrusion would be co-fired with thevia platinum fill 186. In the embodiment illustrated in FIG. 43, thewire bond pad 252 would be gold brazed with a gold braze pre-form (notshown) to make a solid mechanical and electrical contact between thebottom of the wire bond pad 252 and the via hole 186.

FIG. 44 is nearly identical to FIG. 43 except that the castellations 254have been made larger (into a square shape) and the corresponding wirebond pad 252 has also been made square. This structure would be muchmore robust during compressing welding operations during attachment ofleadwires 118 where substantial force is pressed against the wire bondpad. Referring once again to FIG. 44, one can see that the wire bondpads 252 have a co-machined or co-formed post 256. This post would slipdown into the via hole paste 186 and be co-fired. An ideal material forCTE match would, therefore, be a platinum post; however, gold, titanium,tantalum, palladium can all be used.

FIG. 45 is similar to FIGS. 43 and 44 except that the L-shaped wire bondpad 258 has a threaded hole 260. There is a hole 264 to receiveleadwires 118 coming from the header block connector assembly. A setscrew 262, which may have an Allen head or the like, is used to firmlysecure the leadwire 118 into the wire bond pad hole 264. The wire bondpad 258 is attached to the via holes 186 by means of electricalconnection material 226, which has been previously described.

FIG. 46 illustrates a different type of header block connector assembly268 which has an insertable contact spring 270. This allows the co-firedhigh purity alumina (Al₂O₃) hermetic terminal subassembly 189 with oneor more pure platinum filled vias 186 of the present invention to beformed and then the header block connector assemblies to be attached bysimple mechanical force insertion. This is best understood by referringto FIGS. 47 and 48, which are sectional views taken from FIG. 46. Onecan see that the insertable contact spring 270 has been inserted abouthalf way down into the via hole. The bottom of the via hole is co-firedpure platinum in accordance with the present invention and forms ahermetic terminal subassembly 189 (FIG. 49).

FIG. 48 is a sectional view 48-48 taken from FIG. 47 and illustrates theinsertable contact spring 270 inserted into the bore hole. Importantly,the bore hole is first metalized with an adhesion layer 272 and awetting layer 274. These layers could be actually merged into a singlelayer in the case where gold or platinum was sputtered on. Or, anadhesion layer of titanium could be used with a niobium or molybdenumlayer 274 sputtered on top. In a preferred embodiment, the insertablecontact spring 270 would be of Nitinol alloy. At relatively coldtemperature, the insertable Nitinol spring 270 would shrink down andcontract. This memory shaped alloy would be designed in this applicationto expand rapidly at room temperature and, therefore, mechanically fitvery securely into the via hole. This would, of course, be true both atroom temperature 25° C. and at body temperature 37° C. As it turns out,the entire assembly is easily reworkable. All one would have to do ischill it down, say to around freezing temperature, and then literallyall the Nitinol leadwires would contract and insertable leadwires 270could easily be pulled out. Leadwire 118 coming from the header blockconnector assembly (not shown) could either be laser welded to the endof a connector block or, as is shown in FIG. 46, could be slipped into ahole 264. There is a convenient side hole 266 wherein a laser weld couldbe performed to make a secure electrical and mechanical attachmentbetween the leadwire 118 and the header block connector assembly 268.

FIG. 49 is the same as a combination of the co-fired high purity alumina(Al₂O₃) hermetic terminal subassembly 189 with one or more pure platinumfilled vias 186 previously described in FIG. 30 and FIG. 46. In thiscase, the wire connector blocks 268 have a hole 264, as previouslydescribed in FIG. 46, for convenient reception of leadwire 118 from theheader block connector assembly (not shown). The header block connectorassembly 268 has a hole 276 which is designed to be aligned directlyover the platinum filled via holes 186. An electrical connection 226 isthen made either by gold brazing, thermal-setting conductive adhesives,or the like. A laser weld access hole 266 is used to laser weld the pin118 to the inside of the header block connector assembly 268 hole 264.

FIGS. 50 through 56 show alternative embodiments of the header blockconnector assemblies such as those previously illustrated in FIGS. 46and 49. FIGS. 50 and 50A illustrate stampings, which are ideally ofplatinum or some other similar biocompatible material. They have a holefor convenient reception of leadwire 118 which may then be permanentlyattached by laser welding.

FIG. 51 is a sectional view 51-51 taken from FIG. 50A showing thestamping and cross-section.

FIG. 52 is a sectional view showing the stamping of FIGS. 50, 50A and 51co-fired into the novel platinum filled via 186 of the presentinvention.

FIGS. 53 and 53A illustrate another embodiment of stamping 268 b nowwith fingers 265 that capture the leadwire 118.

FIG. 54 is an alternative embodiment for the header block connectorassembly 268 c, which in this case, has a leadwire 278. The leadwire maybe attached to the bracket 268 c by laser welding or the entire assemblycould be co-machined or even formed by metal injection processes. Inthis case, the leadwire is a platinum or suitable biocompatible materialthat has a CTE that will match that of the platinum filled via 186. Inthis case, the leadwire 278 is co-fired with the platinum filled viamaterial 186 to form a solid electrical and mechanical joint.

FIG. 55 is similar to FIG. 54 except that the header block connectorassembly 268 d has a convenient hole 264 for insertion of the leadwire118 (not shown) where it can be laser welded.

FIG. 56 is similar to FIG. 54 except that the header block connectorassembly 268 e shows where the leadwire 278 has been gold brazed 280 tothe via hole pure platinum material 186.

FIG. 57 illustrates a co-fired high purity alumina (Al₂O₃) hermeticterminal subassembly 189 with one or more pure platinum filled vias 186with brazed wire bond pads 252. There are internal circuit traces 282which are exposed on edge where each of the header block connectorassemblies 252 are to be attached. There is a metallization added 284such as a gold or a platinum sputtering over a titanium bonding layer.When the metallization 284 is on the device side (not shown), thoseskilled in the art could use a variety of materials beyond gold andplatinum. There is a gold pre-form 286 that is disposed between theheader block connector assembly 252 and the metallization 284.

FIG. 58 is a sectional view taken from section 58-58 of FIG. 57illustrating the gold braze pre-form 286 after it has been melted athigh temperature to make a solid electrical and mechanical connectionbetween the header block connector assembly 252 and the metallization284. The metallization 284 desirably connects the circuit traces 282 inparallel. In another embodiment (not shown) it is possible to use adispensable gold paste in lieu of the gold braze pre-form to act as asort of “mortar” to bind components.

FIG. 59 is taken from section 59-59 of FIG. 57 and illustrates analternative form of the header block connector assembly 252. In thiscase, the header block connector assembly has been hollowed out, thatis, a void or opening was made in the header block connector assembly tohold a gold braze pre-form 286 for attachment, at high temperature, tometallization 284.

FIG. 60 illustrates a co-fired high purity alumina (Al₂O₃) hermeticterminal subassembly 189 with one or more pure platinum filled vias 186of the present invention wherein, leadwires 118 have been co-fired intothe platinum filled vias 186. In other words, the leadwire 118 isco-fired with the alumina 188 and with the platinum filled via 186, allin one single operation. Leadwires 118 would be routed and connected toimplantable lead conductors or header block connector assemblies, as iswell known in the prior art. As an alternative to a platinum leadwire118, the leadwire 118 may comprise iridium, rhodium, niobium if areducing atmosphere is used or palladium in air if the sinteringtemperature is low enough.

FIG. 61 illustrates an alternative embodiment for the co-fired highpurity alumina (Al₂O₃) hermetic terminal subassembly 189 with one ormore pure platinum filled vias 186 of the present invention. In thiscase, there are internal circuit traces 282. The alumina ceramic bodythen is laid down in tape layers 188 where the upper layers aremetalized to form the circuit traces 282 which contact header blockconnector assemblies 252, as previously described in FIG. 57. In thiscase, the platinum filled via holes 186 are blind holes, in that theplatinum does not penetrate all the way through to the top. These blindholes are important in this case, since the high purity alumina ceramic188 now completely surrounds the via holes 186. Electrical continuity isprovided from the platinum filled via hole 186 to circuit traces 282,which are in turn connected to wire bond pad 252 and to leadwires 118.It will be understood by those skilled in the art that leadwires 118 maybe directly routed to implanted lead conductors, to distal electrodes orto header block connector assemblies which facilitate insertion of animplantable lead.

FIG. 62 is similar to FIG. 59 except that the via holes 186 and 186′have been staggered. They have a section of circuit trace 287 betweenthe stagger. This is a way of increasing the reliability and thehermeticity of the overall terminal subassembly.

FIG. 63 is similar to FIG. 62 in that there are staggered vias 186 and186′ that are filled with pure platinum. In this case, platinumleadwires 118 have been co-fired into the upper vias 186′. As previouslystated, these leadwires 118 could be routed to implanted leads, toimplanted distal electrodes or header block connector assemblies ofAIMDs.

FIG. 64 illustrates the co-firing of a novel crimp post 288 into theplatinum filled via 186. Ideally, the crimp post would be of platinum orsimilar biocompatible material, which would have a CTE which closelymatches that of platinum. A leadwire 118 (not shown) would be insertedinto the crimp post and then a mechanical crimping tool would be used toform a mechanical and electrical connection between the walls of thecrimp post and the lead 118. An optional or supplementary laser weldcould also be performed at the point where the leadwire 118 is insertedinto the top of the crimp post 288.

FIG. 65 is similar to FIG. 64, but illustrates a double crimp post. Onthe body fluid side, lead 118 is crimped into the crimp post 290 asshown. On the device inside, a wire 118′ can be inserted and crimpedinto the opposite side 291 of the crimp post 290 to make connection tointernal AIMD circuits. As described before, leadwire 118′ could be aninexpensive copper insulated leadwire or, as in this case, a bareleadwire.

FIG. 66 illustrates a novel method of header block connector assemblyattachment. The header block connector assembly 104 has been completelyprefabricated in accordance with the present invention and has leadwires118 extending down into a novel window 210 of the present invention.Co-molded or co-formed with the header block connector assembly 104 is asupport structure 302. The header block connector assembly 104 is showntilted 90°. There is a co-fired high purity alumina (Al₂O₃) hermeticterminal subassembly 189 with one or more pure platinum filled vias 186of the present invention with novel wire bond post 294. These wire bondposts 294 each have a leadwire protrusion which are inserted into thevia holes and are co-fired with the pure platinum 186. The supportstructure 302 is designed to slip between the two rows of bonding posts294 and provide back support for them. That is, when one pushes againstleadwire 118 very firmly with a resistance welder, this will prevent aplatinum or equivalent post (which are very ductile) from deforming.

FIG. 67 illustrates a different type of post 296 which could be used inFIG. 66. Post 296 has a novel slot 298 which can receive leadwire 118where a laser weld 300 or the like can be performed.

FIG. 68 illustrates a layered co-fired high purity alumina (Al₂O₃)hermetic terminal subassembly with one or more filled vias 304 designedfor greater connection density in a neurostimulator or other type ofAIMD. This type of high density stacking arrangement is particularlyuseful in conjunction with the window 210 previously described in novelheader block connector assembly in FIG. 28.

FIG. 69 is a cross-sectional view taken generally from section 69-69 ofFIG. 68. FIG. 69 illustrates vias 304 along with circuit traces 282 thatmake contact to the header block connector assemblies 252. It will beappreciated that there is a metallization and gold braze (not shown)that connects the header block connector assemblies 252 to the circuittraces 282. The body of the co-fired high purity alumina (Al₂O₃)hermetic terminal subassembly with one or more filled vias 304, asillustrated in FIG. 69, is of high purity alumina 188. The via hole 304may be filled with pure platinum or a less expensive material, such astungsten or the like. In this case, the via holes are never exposed tobody fluid therefore, less expensive materials can be used. It isimportant that the circuit traces 282 be of platinum or similarbiocompatible material since there is some exposure on the body fluidside where the wire bond pads 252 appear. Not shown is a ferrule 122 ormeans of installing this assembly into a prior art AIMD housing 102. Anyof the ferrule or connection structures in any of the previous drawingscan, of course, be adapted to the structure illustrated in FIGS. 68 and69.

FIGS. 70 and 71 are similar to FIG. 68 except that they show alternativestacking methodologies.

FIG. 72 is similar to FIG. 28 except that the hermetic terminalsubassembly of the present invention has a side attachment wire bond pad192 where leadwires 118 are routed from header block connectorassemblies 106 and 106′. These leadwires 118 are attached by laserwelding, or the like, to the side of the hermetic terminal subassemblyextension 214.

FIG. 73 illustrates a co-fired high purity alumina (Al₂O₃) hermeticterminal subassembly 189 with one or more pure platinum filled vias 186of the present invention with a novel crimp post 288 similar to thatpreviously illustrated in FIGS. 64 and 65. In this case, the crimp post288 is designed to receive an external leadwire 118 on the body fluidside. On the opposite side is the nail head structure 306, which in thiscase is radiused. In this case, the crimp post assembly 288 is ideallyof platinum or similar material and is co-fired into the platinum filledvia 186 in accordance with the present invention. A feedthroughcapacitor 124 is attached using a solder BGA structure 202. It will beobvious to those skilled in the art that any of the BGA attachments asillustrated herein could also be solder dots, solder bumps or dots ofthermal-setting conductive adhesives or epoxies, or the like. In apreferred embodiment, material 202 could be of thermal-settingconductive polyimide.

FIGS. 74 through 78 show alternative embodiments of the crimp posts 288previously illustrated in FIG. 72. FIG. 74 illustrates the end view ofthe nail head 306 as previously illustrated in FIG. 73. FIGS. 75 through78 illustrate alternative embodiments of the nail head structure 288having respective nail head ends 306 a through 306 d.

FIG. 79 illustrates a novel header block connector assembly 104 withleadwires 118 routed to connector ports (not shown). Shown are novelsprings 308, which push against a contact post 310. Contact posts 310are designed to be pressed firmly against the novel platinum filled viaholes 186 of the present invention. There is also a methodology offirmly attaching the header block connector assembly 104 to thepacemaker housing 102 (not shown).

FIG. 80 shows an alternative type of novel header block connectorassembly 104 with leadwires 118 that are designed to be routed toconnectors (not shown). In this case, they are laser welded 313 to theplatinum filled vias 186. This is better understood by referring to theenlarged drawing FIG. 81, which is taken from section 81-81 of FIG. 80.This view is taken at 90° to the view shown in FIG. 80. As one can see,the AIMD housing 102 is much narrower. In the header block connectorassembly 104, there are novel access holes 312 so a laser can bedirected and make an electrical connection between the lead 118 and theplatinum filled via 186. In this case, a wire bond pad and gold brazehas been previously attached to the platinum post 186 as has beendescribed in previous drawings.

FIG. 82 illustrates the cross-section of a novel header block connectorassembly port 104, which is attached to an AIMD housing 102. Shown is abipolar connector similar to IS-1 or DF-1 106. Previous FIG. 3illustrates a typical prior art header block connector assembly 104 withsuch ports 106 and 106′. Novel springs 314 in FIG. 82 make electricalcontact to the two terminals of the bipolar connector and also makemechanical and electrical contact against the novel platinum filled vias186 of the present invention.

FIG. 83 is similar to FIG. 82 except that the bipolar connections to theheader block connector assembly port 106 are routed to a female push pinheader block connector assembly 316. The male connectors 318 aredesigned to be firmly inserted into place. The material 316 is flexedoutward as the male portion 318 is pushed in so that after insertion, itforms a firm mechanical and electrical connection. The male posts areco-fired into the platinum filled vias of the present invention asshown. The male 318 and female 316 connectors must be made from abiocompatible material such as platinum, platinum-iridium, palladium,palladium-iridium alloys, palladium-rhodium alloys or niobium alloys.

Although several embodiments have been described in detail for purposesof illustration, various modifications may be made to each withoutdeparting from the scope and spirit of the invention. Accordingly, theinvention is not to be limited, except as by the appended claims.

What is claimed is:
 1. A filter feedthrough assembly, comprising: a) ahermetic feedthrough, comprising: i) an insulator of electricallynon-conductive material defined by an insulator sidewall having an outerinsulator surface extending along a first length from a first insulatorend to a second insulator end; ii) at least one insulator via defined byan insulator bore extending along a second length that is less than thefirst length, wherein the insulator via extends from a first via endspaced from the first insulator end to a second via end at the secondinsulator end; iii) an internal circuit trace extending from theinsulator bore to the outer insulator surface, wherein the circuit traceis spaced from the first and second insulator ends; iv) a conductivefill disposed within the insulator via, wherein the conductive fillforms both a hermetic seal with the insulator bore and an electricallyconductive path extending from the internal circuit trace to a secondconductive fill end at the second insulator end; and v) a ferrule of anelectrically conductive material comprising a ferrule opening defined bya surrounding ferrule sidewall having an inner ferrule surface, whereinthe insulator is hermetically sealed in the ferrule opening; b) afeedthrough capacitor, comprising: i) a dielectric body defined by adielectric sidewall having an outer dielectric surface extending from afirst dielectric end to a second dielectric end; ii) at least one activeelectrode plate and at least one ground electrode plate supported in thedielectric body in spaced relation with each other; iii) at least onedielectric via defined by a dielectric bore extending through thedielectric body to the first and second dielectric ends; iv) an innermetallization disposed on the dielectric bore in electrical contact withthe at least one active electrode plate; and v) an outer metallizationdisposed on an outer surface of the dielectric body in electricalcontact with the at least one ground electrode plate; c) a conductiveleadwire extending from a first leadwire portion having a first leadwireend to a second leadwire end, wherein the first leadwire portion isdisposed within the dielectric via with the first leadwire end locatedin contact with or adjacent to the second conductive fill end; d) anelectrically conductive material at least partially filled in thedielectric via to physically and electrically connect: i) the firstleadwire portion to the inner metallization electrically connected tothe at least one active electrode plate; and ii) the first leadwire endto the second conductive fill end; and e) an outer ground conductivematerial electrically connecting the outer metallization in electricalcontact with the at least one ground plate at the outer dielectricsurface to the ferrule.
 2. The filter feedthrough assembly of claim 1,wherein the electrically conductive material at least partially filledin the dielectric via is selected from the group consisting of a solder,an epoxy, a low temperature braze, a conductive glass frit, and a weld.3. The filter feedthrough assembly of claim 1, wherein the hermetic sealformed by the conductive fill contacting the insulator bore has a leakrate no greater than 1×10⁻⁷ std cc He/sec.
 4. The filter feedthroughassembly of claim 1, wherein the conductive fill disposed in theinsulator via comprises a substantially closed pore and fritlessplatinum fill.
 5. The filter feedthrough assembly of claim 4, whereinthe hermetic seal formed by the conductive fill contacting the insulatorbore is a tortuous and mutually conformal knitline between the insulatorand the platinum fill.
 6. The filter feedthrough assembly of claim 5,wherein the knitline comprises a glass that is at least about 60%silica.
 7. The filter feedthrough assembly of claim 1, wherein thedielectric body comprises at least 96% alumina.
 8. The filterfeedthrough assembly of claim 1, wherein the dielectric body comprisesat least 99% alumina.
 9. The filter feedthrough assembly of claim 1,wherein the outer metallization comprises an adhesion metallizationdisposed on the outer surface of the dielectric body.
 10. The filterfeedthrough assembly of claim 9, wherein the outer metallizationcomprises a wetting metallization disposed on the adhesionmetallization.
 11. The filter feedthrough assembly of claim 1, includinga gold braze hermetically sealing the outer insulator surface to theferrule.
 12. The filter feedthrough assembly of claim 11, wherein thegold braze hermetically sealing the outer insulator surface to theferrule has a leak rate no greater than 1×10⁻⁷ std cc He/sec.
 13. Thefilter feedthrough assembly of claim 1, wherein an insulative washer isdisposed between the insulator of the hermetic feedthrough and thedielectric body of the feedthrough capacitor.
 14. The filter feedthroughassembly of claim 1, wherein the dielectric via extending through thedielectric body to the first and second dielectric ends is staggered.15. The filter feedthrough assembly of claim 1, wherein the insulatorcomprises an elevated insulator portion extending outwardly from theferrule opposite the feedthrough capacitor, and wherein a leadwirecontact is electrically coupled to the circuit trace at the outerinsulator surface, but spaced from the ferrule, the contact beingconfigured for direct electrical connection to a leadwire.
 16. Thefilter feedthrough assembly of claim 15, wherein the leadwire contactcomprises a wire bond pad.
 17. The filter feedthrough assembly of claim15, including a braze preform physically and electrically coupling theleadwire contact to the circuit trace.
 18. A hermetic feedthrough,comprising: a) an insulator of electrically non-conductive materialdefined by an insulator sidewall having an outer insulator surfaceextending along a first length from a first insulator end to a secondinsulator end; b) at least one insulator via defined by an insulatorbore extending along a second length that is less than the first length,wherein the insulator via extends from a first via end spaced from thefirst insulator end to a second via end at the second insulator end; c)an internal circuit trace extending from the insulator bore to the outerinsulator surface, wherein the circuit trace is spaced from the firstand second insulator ends; d) a conductive fill disposed within theinsulator via, wherein the conductive fill forms both a hermetic sealwith the insulator bore and an electrically conductive path extendingfrom the internal circuit trace to a second conductive fill end at thesecond insulator end; and e) a ferrule of an electrically conductivematerial comprising a ferrule opening defined by a surrounding ferrulesidewall having an inner ferrule surface, wherein the insulator ishermetically sealed in the ferrule opening.
 19. A filter feedthroughassembly, comprising: a) a hermetic feedthrough, comprising: i) aninsulator of electrically non-conductive material defined by aninsulator sidewall having an outer insulator surface extending along afirst length from a first insulator end to a second insulator end; ii)at least one active insulator via defined by an active insulator boreextending along a second length that is less than the first length,wherein the active insulator via extends from a first active via endspaced from the first insulator end to a second active via end at thesecond insulator end; iii) an internal circuit trace extending from theactive insulator bore to the outer insulator surface, wherein thecircuit trace is spaced from the first and second insulator ends; iv) anactive conductive fill disposed within the active insulator via, whereinthe active conductive fill forms both a hermetic seal with the activeinsulator bore and an electrically conductive path extending from theinternal circuit trace to a second active conductive fill end at thesecond insulator end; v) at least one ground insulator electrode platesupported by the insulator; vi) at least one ground insulator viadefined by a ground insulator bore extending to the first and secondinsulator ends; vii) a ground conductive fill disposed within the groundinsulator via, wherein the ground conductive fill forms both a hermeticseal with the ground insulator bore and an electrically conductive pathextending to first and second ground fill ends located adjacent to therespective first and second insulator ends, wherein the ground insulatorplate extends from the outer insulator surface and is electricallycoupled to the ground conductive fill, but in a non-conductive relationwith the active conductive fill; viii) an outer metallization disposedon the outer insulator surface in electrical contact with the at leastone ground insulator electrode plate; and ix) a ferrule of anelectrically conductive material comprising a ferrule opening defined bya surrounding ferrule sidewall having an inner ferrule surface, whereinthe insulator is supported in the ferrule opening; b) a feedthroughcapacitor, comprising: i) a dielectric body defined by a dielectricsidewall having an outer dielectric surface extending from a firstdielectric end to a second dielectric end; ii) at least one activeelectrode plate and at least one ground electrode plate supported in thedielectric body in spaced relation with each other; iii) at least oneactive dielectric via defined by an active dielectric bore extendingthrough the dielectric body to the first and second dielectric ends; iv)at least one ground dielectric via defined by a ground dielectric boreextending through the dielectric body to the first and second dielectricends; v) an active inner metallization disposed on the active dielectricbore in electrical contact with the at least one active electrode plate;and vi) a ground inner metallization disposed on the ground dielectricbore in electrical contact with the at least one ground electrode plate;c) an active conductive leadwire having a length extending from a firstactive leadwire portion having a first active leadwire end to a secondactive leadwire end, wherein the first active leadwire portion isdisposed within the active dielectric via with the first active leadwireend located in contact with or adjacent to the second active conductivefill end in the active insulator bore; d) an active electricallyconductive material at least partially filled in the active dielectricvia to physically and electrically connect: i) the first active leadwireportion to the active inner metallization electrically connected to theat least one active electrode plate; and ii) the first active leadwireend to the second active conductive fill end; e) a ground conductiveleadwire having a length extending from a first ground leadwire portionhaving a first ground leadwire end to a second ground leadwire end,wherein the first ground leadwire portion is disposed within the grounddielectric via with the first ground leadwire end located in contactwith or adjacent to the second ground conductive fill end in the groundinsulator bore; f) an inner ground electrically conductive material atleast partially filled in the ground dielectric via to physically andelectrically connect: i) the first ground leadwire portion to the groundinner metallization electrically connected to the at least one groundelectrode plate in the dielectric body; and ii) the first groundleadwire end to the second ground conductive fill end; and g) an outerground conductive material electrically and hermetically connecting theouter metallization in electrical contact with the at least one groundinsulator plate at the outer insulator surface to the ferrule.
 20. Thefilter feedthrough assembly of claim 19, wherein the active and groundelectrically conductive materials at least partially filled in therespective active and ground dielectric vias are selected from the groupconsisting of a solder, an epoxy, a low temperature braze, a conductiveglass frit, and a weld.
 21. The filter feedthrough assembly of claim 19,wherein the hermetic seals formed by the active and ground conductivefills contacting the respective active and ground insulator bores haveleak rates no greater than 1×10⁻⁷ std cc He/sec.
 22. The filterfeedthrough assembly of claim 19, wherein the active and groundconductive fills disposed in the respective active and ground insulatorvias each comprise a substantially closed pore and fritless platinumfill.
 23. The filter feedthrough assembly of claim 19, wherein thehermetic seals formed by the active and ground conductive fillscontacting the respective active and ground insulator bores arecharacterized as tortuous and mutually conformal knitlines between theinsulator and the platinum fills.
 24. The filter feedthrough assembly ofclaim 23, wherein the knitlines each comprise a glass that is at leastabout 60% silica.
 25. The filter feedthrough assembly of claim 19,wherein the dielectric body comprises at least 96% alumina.
 26. Thefilter feedthrough assembly of claim 19, wherein the dielectric bodycomprises at least 99% alumina.
 27. The filter feedthrough assembly ofclaim 19, wherein the outer metallization comprises an adhesionmetallization disposed on the outer insulator surface and a wettingmetallization disposed on the adhesion metallization.
 28. The filterfeedthrough assembly of claim 19, the outer ground conductive materialelectrically and hermetically connecting the outer metallization inelectrical contact with the at least one ground insulator plate at theouter insulator surface to the ferrule is a gold braze.